Freescale MC68HC908KX8MDW M68hc08 microcontroller Datasheet

MC68HC908KX8
MC68HC908KX2
MC68HC08KX8
Data Sheet
M68HC08
Microcontrollers
MC68HC908KX8
Rev. 2.1
07/2005
freescale.com
MC68HC908KX8
MC68HC908KX2
MC68HC08KX8
Data Sheet
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This product incorporates SuperFlash® technology licensed from SST.
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MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
3
Revision History
The following revision history table summarizes changes contained in this document. For your
convenience, the page number designators have been linked to the appropriate location.
Revision History
Date
Revision
Level
Page
Number(s)
Description
Label for pin 9 corrected in Figure 1-1 and Figure 1-2
19, 20
$FF is the erase state of the FLASH, not $00.
April,
2001
February,
2002
0.1
1.0
82, 252, 255
First bulleted paragraph under the subsection 15.5 Interrupts reworded
for clarity
177
Revision to the description of the CHxMAX bit and the note that follows
that description
183
Forced monitor mode information added to Table 16-1.
192
In Figure 16-10. Monitor Data Format, resistor value for connection
between VTST and IRQ1 changed from 10 kΩ to 1 kΩ.
194
7.2 Features — Corrected third bullet
71
7.7.3 ICG Trim Register — Corrected description of the TRIM7:TRIM0
bits
97
14.2 Features — Corrected divide by factors in first bullet
165
Figure 14-1. Timebase Block Diagram — Corrected
divide-by-2 blocks
166
Table 14-1. Timebase Divider Selection — Corrected last divider tap
entry
167
Section 15. Timer Interface Module (TIM) — Timer discrepancies
corrected throughout this section
169
17.4 Thermal Characteristics — Corrected SOIC thermal resistance and
maximum junction temperature
202
17.5 5.0-Vdc DC Electrical Characteristics and — Corrected footnote
for VDD supply current in stop mode
203 and 204
Appendix B. MC68HC08KX8 — Added to supply exception information
for the MC68HC08KX8
215
Reformatted to current publication standards
March,
2004
2.0
Throughout
2.7 FLASH Page Erase Operation — Updated procedure
33
2.8 FLASH Mass Erase Operation — Updated procedure
33
2.9 FLASH Program/Read Operation — Updated procedure
34
Figure 5-1. COP Block Diagram — Updated figure
53
Table 6-1. Instruction Set Summary — Added WAIT instruction
69
Section 7. Internal Clock Generator Module (ICG) — Updated with new
information
July,
2005
2.1
71 through 98
14.2 Features — Corrected values given in the first bullet
165
Table 15-3. Mode, Edge, and Level Selection — Reworked for clarity
182
17.11 Memory Characteristics — Updated table with new information
210
Updated to meet Freescale identity guidelines.
Throughout
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
4
Freescale Semiconductor
List of Chapters
Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chapter 2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Chapter 3 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Chapter 4 Configuration Register (CONFIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Chapter 5 Computer Operating Properly Module (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Chapter 6 Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Chapter 7 Internal Clock Generator Module (ICG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Chapter 8 External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Chapter 9 Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Chapter 10 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Chapter 11 Input/Output (I/O) Ports (PORTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Chapter 12 Serial Communications Interface Module (SCI) . . . . . . . . . . . . . . . . . . . . . . .111
Chapter 13 System Integration Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Chapter 14 Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Chapter 15 Timer Interface Module (TIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Chapter 16 Development Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
Chapter 17 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
Chapter 18 Ordering Information and Mechanical Specifications . . . . . . . . . . . . . . . . . . 193
Appendix A MC68HC908KX2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195
Appendix B MC68HC08KX8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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List of Chapters
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
6
Freescale Semiconductor
Table of Contents
Chapter 1
General Description
1.1
1.2
1.3
1.4
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Supply Pins (VDD and VSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oscillator Pins (OSC1 and OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Interrupt Pin (IRQ1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port A Input/Output (I/O) Pins (PTA4/KBD4–PTA0/KBD0) . . . . . . . . . . . . . . . . . . . . . . . . .
Analog Reference Pin (VREFH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port B Input/Output (I/O) Pins (PTB7/(OSC2)/RST–PTB0/AD0) . . . . . . . . . . . . . . . . . . . . .
17
17
18
20
20
21
21
21
21
21
Chapter 2
Memory
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
2.12
2.13
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Monitor ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Page Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Program/Read Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Block Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Block Protect Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
23
23
31
31
31
32
33
34
36
36
37
37
Chapter 3
Analog-to-Digital Converter (ADC)
3.1
3.2
3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Continuous Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accuracy and Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
39
39
39
39
41
41
42
42
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Table of Contents
3.4
3.5
3.5.1
3.5.2
3.6
3.6.1
3.6.2
3.7
3.7.1
3.7.2
3.7.3
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Analog Power and ADC Voltage Reference Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Voltage In (ADCVIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Input Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
42
42
42
42
43
43
43
43
43
45
45
Chapter 4
Configuration Register (CONFIG)
4.1
4.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Chapter 5
Computer Operating Properly Module (COP)
5.1
5.2
5.3
5.4
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
5.4.6
5.4.7
5.4.8
5.5
5.6
5.7
5.8
5.8.1
5.8.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reset Vector Fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
51
51
52
52
52
52
52
52
52
53
53
53
53
53
53
53
53
54
Chapter 6
Central Processor Unit (CPU)
6.1
6.2
6.3
6.3.1
6.3.2
6.3.3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
55
55
55
56
56
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MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
8
Freescale Semiconductor
6.3.4
6.3.5
6.4
6.5
6.5.1
6.5.2
6.6
6.7
6.8
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
57
58
59
59
59
59
59
60
65
Chapter 7
Internal Clock Generator Module (ICG)
7.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.1
Clock Enable Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.2
Internal Clock Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.2.1
Digitally Controlled Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.2.2
Modulo "N" Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.2.3
Frequency Comparator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.2.4
Digital Loop Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.3
External Clock Generator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.3.1
External Oscillator Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.3.2
External Clock Input Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.4
Clock Monitor Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.4.1
Clock Monitor Reference Generator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.4.2
Internal Clock Activity Detector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.4.3
External Clock Activity Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.5
Clock Selection Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.5.1
Clock Selection Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.5.2
Clock Switching Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4
Usage Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.1
Switching Clock Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.2
Enabling the Clock Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.3
Using Clock Monitor Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.4
Quantization Error in DCO Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.4.1
Digitally Controlled Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.4.2
Binary Weighted Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.4.3
Variable-Delay Ring Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.4.4
Ring Oscillator Fine-Adjust Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.5
Switching Internal Clock Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.6
Nominal Frequency Settling Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.6.1
Settling To Within 15% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.6.2
Total Settling Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.7
Trimming Frequency on the Internal Clock Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
67
67
67
69
69
70
70
70
71
71
71
72
73
73
75
75
76
77
77
77
78
78
79
80
80
80
81
81
81
81
82
82
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7.5
7.5.1
7.5.2
7.6
7.6.1
7.6.2
7.6.3
7.6.4
7.7
7.7.1
7.7.2
7.7.3
7.7.4
7.7.5
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CONFIG (or MOR) Register Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Clock Enable (EXTCLKEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Crystal Enable (EXTXTALEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Slow External Clock (EXTSLOW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oscillator Enable In Stop (OSCENINSTOP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ICG Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ICG Multiplier Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ICG Trim Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ICG DCO Divider Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ICG DCO Stage Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
83
83
84
84
84
84
85
85
85
87
88
89
89
89
Chapter 8
External Interrupt (IRQ)
8.1
8.2
8.3
8.4
8.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IRQ1 Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IRQ Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
91
91
91
93
94
Chapter 9
Keyboard Interrupt Module (KBI)
9.1
9.2
9.3
9.4
9.5
9.5.1
9.5.2
9.6
9.6.1
9.6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Keyboard Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Keyboard Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Chapter 10
Low-Voltage Inhibit (LVI)
10.1
10.2
10.3
10.3.1
10.3.2
10.3.3
10.3.4
10.4
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltage Hysteresis Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LVI Trip Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LVI Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
101
101
101
102
102
102
102
103
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10.5 LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
103
103
103
103
Chapter 11
Input/Output (I/O) Ports (PORTS)
11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2 Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.1
Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.2
Data Direction Register A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.3
Port A Input Pullup Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.3 Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.3.1
Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.3.2
Data Direction Register B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
105
106
106
106
107
108
108
109
Chapter 12
Serial Communications Interface Module (SCI)
12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.1
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2.4
Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2.5
Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2.6
Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.2
Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.5
Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.6
Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.7
Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.3.8
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6.1
TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6.2
RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
111
111
113
113
113
115
115
115
117
117
117
117
118
119
119
119
121
121
123
123
123
124
124
124
124
124
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12.7 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
12.7.1
SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
12.7.2
SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
12.7.3
SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
12.7.4
SCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
12.7.5
SCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
12.7.6
SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
12.7.7
SCI Baud Rate Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Chapter 13
System Integration Module (SIM)
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2 SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.2
Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3
Clocks in Stop Mode and Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1.1
Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1.2
Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1.3
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1.4
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1.5
Forced Monitor Mode Entry Reset (MENRST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1.6
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4 SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.1
SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.2
SIM Counter During Stop Mode Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4.3
SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.5 Program Exception Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.5.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.5.1.1
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.5.1.2
SWI Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.5.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7.1
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7.2
Interrupt Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7.2.1
Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7.2.2
Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7.2.3
Interrupt Status Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
137
139
139
139
139
140
140
141
141
141
142
142
142
142
142
142
142
143
143
144
145
145
145
146
147
148
148
149
149
150
150
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Chapter 14
Timebase Module (TBM)
14.1
14.2
14.3
14.4
14.5
14.6
14.6.1
14.6.2
14.7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TBM Interrupt Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Timebase Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
151
151
151
151
153
153
153
153
154
Chapter 15
Timer Interface Module (TIM)
15.1
15.2
15.3
15.4
15.4.1
15.4.2
15.4.3
15.4.4
15.4.5
15.4.6
15.4.7
15.4.8
15.4.9
15.5
15.6
15.6.1
15.6.2
15.7
15.8
15.8.1
15.8.2
15.8.3
15.8.4
15.8.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TIM Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pulse-Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TIM Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TIM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TIM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TIM Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TIM Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
155
155
155
155
158
158
158
159
159
159
160
161
161
162
162
162
162
162
163
163
164
165
165
168
Chapter 16
Development Support
16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.1.1
Flag Protection During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.1.2
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
169
169
169
169
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Table of Contents
16.2.1.3
TIM1 and TIM2 During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.1.4
COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.2
Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.2.1
Break Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.2.2
Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.2.3
Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.2.4
Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.2.5
Break Auxiliary Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.3
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.3.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.3.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3 Monitor ROM (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.1
Monitor Mode Entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.2
Normal Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.3
Forced Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.4
Monitor Mode Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.5
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.6
Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.7
Baud Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.8
Force Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.9
Normal Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1.10
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.2
Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
171
171
171
171
172
172
173
173
173
173
173
174
174
174
174
176
176
177
177
177
177
177
178
181
Chapter 17
Electrical Specifications
17.1
17.2
17.3
17.4
17.5
17.6
17.7
17.8
17.9
17.9.1
17.9.2
17.10
17.11
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.0-Vdc DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.0-Vdc DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internal Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Trimmed Accuracy of the Internal Clock Generator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7-Volt to 3.3-Volt Trimmed Internal Clock Generator Characteristics . . . . . . . . . . . . . . .
4.5-Volt to 5.5-Volt Trimmed Internal Clock Generator Characteristics . . . . . . . . . . . . . . .
Analog-to-Digital Converter (ADC) Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
183
183
184
184
185
186
187
187
188
188
188
191
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Freescale Semiconductor
Chapter 18
Ordering Information and Mechanical Specifications
18.1
18.2
18.3
18.4
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-Pin Plastic Dual In-Line Package (PDIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-Pin Small Outline Package (SOIC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
193
193
194
194
Appendix A
MC68HC908KX2
A.1
A.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Appendix B
MC68HC08KX8
B.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2
FLASH x ROM Module Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.1
FLASH for ROM Substitution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2.2
Partial Use of FLASH-Related Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.3
Configuration Register Programming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.1
Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.2
Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.3
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.4
5.0-Vdc DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.5
3.0-Vdc DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.6
Internal Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.7
External Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.8
Trimmed Accuracy of the Internal Clock Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.8.1
2.7-Volt to 3.3-Volt Trimmed Internal Clock Generator Characteristics . . . . . . . . . . . . .
B.4.8.2
4.5-Volt to 5.5-Volt Trimmed Internal Clock Generator Characteristics . . . . . . . . . . . . .
B.4.9
Analog-to-Digital Converter (ADC) Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.4.10
Memory Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
197
197
197
199
199
201
201
202
202
203
204
205
205
206
206
206
207
207
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
15
Table of Contents
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
16
Freescale Semiconductor
Chapter 1
General Description
1.1 Introduction
The MC68HC908KX8 is a member of the low-cost, high-performance M68HC08 Family of 8-bit
microcontroller units (MCU). The M68HC08 Family is based on the customer-specified integrated circuit
(CSIC) design strategy. All MCUs in the family use the enhanced M68HC08 central processor unit
(CPU08) and are available with a variety of modules, memory sizes and types, and package types.
The information contained is this document pertains to the MC68HC908KX2 and the MC68HC08KX8 with
the exceptions found in:
• Appendix A MC68HC908KX2
• Appendix B MC68HC08KX8
1.2 Features
Features include:
• High-performance M68HC08 architecture
• Fully upward-compatible object code with M6805, M146805, and M68HC05 Families
• Maximum internal bus frequencies of:
– 8 MHz at 5.0 V
– 4 MHz at 3.0 V
• Internal oscillator requiring no external components:
– Software selectable bus frequencies
– 25 percent accuracy with trim capability to 2 percent
– Clock monitor
– Option to allow use of external clock source or external crystal/ceramic resonator
• Eight Kbytes of on-chip, in-circuit programmable FLASH memory
• FLASH program memory security(1)
• On-chip programming firmware for use with host personal computer which does not require high
voltage for entry
• 192 bytes of on-chip random-access memory (RAM)
• 16-bit, 2-channel timer interface (TIM) module
• 4-channel, 8-bit, analog-to-digital converter (ADC) with high-voltage reference (VREFH) double
bonded to VDD pin
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
17
General Description
•
•
•
•
•
•
•
•
•
•
•
Serial communications interface (SCI) module
5-bit keyboard interrupt (KBI) with wakeup feature
13 general-purpose input/output (I/O) ports:
– Five shared with KBI and TIM, with 15-mA source/15-mA sink capabilities and with
programmable pullups on general- purpose input ports
– Four shared with ADC
– Two shared with SCI
Low-voltage inhibit (LVI) module with software selectable trip points, 2.6-V or 4.3-V trip point
Timebase module (TBM) with
– Clock prescaler for eight user-selectable, periodic real-time interrupts
– Active clock source in stop mode for periodic wakeup from stop using external crystal or
internal oscillator
External asynchronous interrupt pin with internal pullup (IRQ1)
System protection features:
– Computer operating properly (COP) reset
– Low-voltage detection with reset
– Illegal opcode detection with reset
– Illegal address detection with reset
16-pin plastic dual in-line (PDIP) or small outline (SOIC) package
Low-power design fully static with stop and wait modes
Internal power-up reset circuit requiring no external pins
–40°C to +125°C operation
Features of the CPU08 include:
• Enhanced HC05 programming model
• Extensive loop control functions
• 16 addressing modes, eight more than the M68HC05
• 16-bit index register and stack pointer
• Memory-to-memory data transfers
• Fast 8 × 8 multiply instruction
• Fast 16/8 divide instruction
• Binary-coded decimal (BCD) instructions
• Optimization for controller applications
• Third party C language support
1.3 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908KX8.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
18
Freescale Semiconductor
PTA0/KBD0(2), (3)
PTA1/KBD1(2), (3)
PTA2/KBD2/TCH0(2), (3)
PTA3/KBD3/TCH1(2), (3)
PTA4/KBD4(2), (3)
POWER-ON RESET
MODULE
CONTROL AND STATUS REGISTERS — 78 BYTES
SECURITY
MODULE
USER FLASH — 7680 BYTES
COMPUTER OPERATING PROPERLY
MODULE
USER RAM — 192 BYTES
PTB
ARITHMETIC/LOGIC
UNIT
DDRB
CPU
REGISTERS
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
PTB5/TxD
PTB6/(OSC1)(4)
PTB7/(OSC2)/RST(4)
PTA
M68HC08 CPU
LOW-VOLTAGE INHIBIT
MODULE
MONITOR ROM — 295 BYTES
2-CHANNEL TIMER INTERFACE
MODULE
USER FLASH VECTOR SPACE — 36 BYTES
KEYBOARD INTERRUPT
MODULE
FLASH BURN-IN ROM — 1024 BYTES
INTERNAL CLOCK GENERATOR
MODULE
(SOFTWARE SELECTABLE)
DDRA
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
INTERNAL BUS
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATION INTERFACE
MODULE
SYSTEM INTEGRATION
MODULE
IRQ
MODULE
IRQ1(1)
VDD
VSS
PROGRAMMABLE TIME BASE
MODULE
BREAK
MODULE
POWER
1. Pin contains integrated pullup resistor
2. High-current source/sink pin
3. Pin contains software selectable pullup resistor if general function I/O pin is configured as input.
Figure 1-1. MC68HC908KX8 MCU Block Diagram
19
MCU Block Diagram
Notes:
General Description
1.4 Pin Assignments
Figure 1-2 shows the pin assignments for MC68HC908KX8.
VSS
1
16
VDD
PTA1/KBD1
2
15
PTA4/KBD4
PTA0/KBD0
3
14
PTA3/KBD3/TCH1
IRQ1
4
13
PTA2/KBD2/TCH0
PTB0/AD0
5
12
PTB4/RxD
PTB1/AD1
6
11
PTB5/TxD
PTB2/AD2
7
10
PTB6/(OSC1)
PTB3/AD3
8
9
PTB7/(OSC2)/RST
Figure 1-2. PDIP and SOIC Pin Assignments
1.4.1 Supply Pins (VDD and VSS)
VDD and VSS are the power supply and ground pins. The MCU operates from a single power supply.
Fast signal transitions on MCU pins place high, short-duration current demands on the power supply. To
prevent noise problems, take special care to provide power supply bypassing at the MCU as shown in
Figure 1-3. Place the bypass capacitors as close to the MCU power pins as possible. Use high-frequency
response ceramic capacitors for CBypass. CBulk are optional bulk current bypass capacitors for use in
applications that require the port pins to source high-current levels.
MCU
VDD
VSS
CBypass
0.1 µF
+
CBulk
VDD
Note: Component values shown represent typical applications.
Figure 1-3. Power Supply Bypassing
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
20
Freescale Semiconductor
Pin Assignments
1.4.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are available through programming options in the configuration register. These
pins then become the connections to an external clock source or crystal/ceramic resonator. PTB7 and
PTB6 are not available for the crystal/ceramic resonator option and PTB6 is unavailable for the external
clock source option.
1.4.3 External Interrupt Pin (IRQ1)
IRQ1 is an asynchronous external interrupt pin with an internal pullup resistor. See Chapter 8 External
Interrupt (IRQ).
1.4.4 Port A Input/Output (I/O) Pins (PTA4/KBD4–PTA0/KBD0)
PTA4/KBD4–PTA0/KBD0 is a 5-bit special-function port that shares its pins with the keyboard interrupt
(KBI) module and the 2-channel timer module (TIM).
• Any or all of the port A pins can be programmed to serve as keyboard interrupt pins. The respective
pin utilizes an internal pullup resistor when enabled. See Chapter 9 Keyboard Interrupt Module
(KBI).
• Each port A pin contains a software selectable internal pullup resistor when the general-function
I/O port is configured as an input. See Chapter 11 Input/Output (I/O) Ports (PORTS). The pullup
resistor is automatically disabled once a TIM special function is enabled for that pin.
• All port A pins are high-current source/sink pins.
NOTE
Any unused inputs and I/O ports should be tied to an appropriate logic level
(either VDD or VSS). Although the I/O ports of the MC68HC908KX8 do not
require termination, termination is recommended to reduce the possibility
of static damage.
1.4.5 Analog Reference Pin (VREFH)
The VREFH pin is the analog reference voltage for the analog-to-digital converter (ADC) module. The
voltage is supplied through a double-bond to the VDD pin. See Chapter 17 Electrical Specifications for
ADC parameters.
1.4.6 Port B Input/Output (I/O) Pins (PTB7/(OSC2)/RST–PTB0/AD0)
PTB7/(OSC2)/RST–PTB0/AD0 are general-purpose bidirectional I/O port pins, all sharing special
functions.
• PTB7 and PTB6 share with the on-chip oscillator circuit through configuration options. See 7.3.3
External Clock Generator.
• PTB5 and PTB4 share with the SCI module. See Chapter 12 Serial Communications Interface
Module (SCI).
• PTB3–PTB0 share with the ADC module. See Chapter 3 Analog-to-Digital Converter (ADC).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
21
General Description
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
22
Freescale Semiconductor
Chapter 2
Memory
2.1 Introduction
The central processor unit (CPU08) can address 64 Kbytes of memory space.
The memory map, shown in Figure 2-1, includes:
• 7680 bytes of FLASH memory
• 192 bytes of random-access memory (RAM)
• 36 bytes of user-defined vectors
• 295 bytes of monitor read-only memory (ROM)
2.2 I/O Registers
Most of the control, status, and data registers are in the zero-page area of $0000–$003F. Additional
input/output (I/O) registers have the following addresses:
• $FE01 — SIM reset status register, SRSR
• $FE04 — Interrupt status register 1, INT1
• $FE05 — Interrupt status register 2, INT2
• $FE06 — Interrupt status register 3, INT3
• $FE08 — FLASH control register, FLCR
• $FE09 — Break address register high, BRKH
• $FE0A — Break address register low, BRKL
• $FE0B — Break status and control register, BRKSCR
• $FE0C — LVI status register, LVISR
• $FF7E — FLASH block protect register, FLBPR
in non-volatile FLASH memory
• $FFFF — COP control register, COPCTL
A summary of the available registers is provided in Figure 2-2. Table 2-1 is a list of vector locations.
2.3 Monitor ROM
The 295 bytes at addresses $FE20–$FF46 are reserved ROM addresses that contain the instructions for
the monitor functions.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
23
Memory
$0000
↓
$003F
$0040
↓
$00FF
$0100
↓
$0FFF
$1000
↓
$13FF
I/O REGISTERS (64 BYTES)
RAM (192 BYTES)
UNIMPLEMENTED (3839 BYTES)
FLASH BURN-IN ROM (1024 BYTES)
$1400
↓
$DFFF
UNIMPLEMENTED (52,224 BYTES)
$E000
↓
$FDFF
USER FLASH MEMORY (7680 BYTES)
$FE00
RESERVED
$FE01
SIM RESET STATUS REGISTER (SRSR)
$FE02
RESERVED
$FE03
RESERVED
$FE04
INTERRUPT STATUS REGISTER 1 (INT1)
$FE05
INTERRUPT STATUS REGISTER 2 (INT2)
$FE06
INTERRUPT STATUS REGISTER 3 (INT3)
$FE07
RESERVED
$FE08
FLASH CONTROL REGISTER (FLCR)
$FE09
BREAK ADDRESS REGISTER HIGH (BRKH)
$FE0A
BREAK ADDRESS REGISTER LOW (BRKL)
$FE0B
BREAK STATUS AND CONTROL REGISTER (BRKSCR)
$FE0C
LVI STATUS REGISTER (LVISR)
$FE0D
↓
$FE1F
UNIMPLEMENTED (18 BYTES)
$FE20
↓
$FF46
MONITOR ROM (295 BYTES)
$FF47
↓
$FF7D
UNIMPLEMENTED (57 BYTES)
$FF7E
FLASH BLOCK PROTECT REGISTER (FLBPR)
$FF7F
↓
$FFDB
UNIMPLEMENTED (90 BYTES)
$FFDC
↓
$FFFF
FLASH VECTORS
(36 BYTES)
Figure 2-1. Memory Map
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
24
Freescale Semiconductor
Monitor ROM
Addr.
$0000
$0001
Register Name
Port A Data Register Read:
(PTA) Write:
See page 106. Reset:
Port B Data Register Read:
(PTB) Write:
See page 108. Reset:
$0002
Unimplemented
$0003
Unimplemented
$0004
Data Direction Register A Read:
(DDRA) Write:
See page 106. Reset:
$0005
$0006
↓
$000C
$000D
$000E
↓
$0012
$0013
$0014
$0015
$0016
Data Direction Register B Read:
(DDRB) Write:
See page 109. Reset:
Bit 7
6
5
0
0
0
4
3
2
1
Bit 0
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
Unaffected by reset
PTB7
PTB6
PTB5
PTB4
PTB3
Unaffected by reset
0
0
0
0
0
DDRB7
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
0
0
0
0
PTAPUE4
PTAPUE3
PTAPUE2
PTAPUE1
PTAPUE0
0
0
0
0
0
0
0
0
LOOPS
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
T8
R
R
ORIE
NEIE
FEIE
PEIE
Unimplemented
Port A Input Pullup Enable Read:
Register (PTAPUE) Write:
See page 108. Reset:
Unimplemented
SCI Control Register 1 Read:
(SCC1) Write:
See page 125. Reset:
SCI Control Register 2 Read:
(SCC2) Write:
See page 127. Reset:
SCI Control Register 3 Read:
(SCC3) Write:
See page 129. Reset:
R8
U
U
0
0
0
0
0
0
SCI Status Register 1 Read:
(SCS1) Write:
See page 130. Reset:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
0
0
0
0
0
0
R
= Reserved
1
= Unimplemented
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 5)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
25
Memory
Addr.
Bit 7
6
5
4
3
2
1
Bit 0
SCI Status Register 2 Read:
(SCS2) Write:
See page 132. Reset:
0
0
0
0
0
0
BKF
RPF
0
0
0
0
0
0
0
0
SCI Data Register Read:
(SCDR) Write:
See page 133. Reset:
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
SCI Baud Rate Register Read:
(SCBR) Write:
See page 133. Reset:
0
0
0
Keyboard Status and Read:
Control Register (KBSCR) Write:
See page 99.
Reset:
0
0
0
0
0
0
0
$001B
Keyboard Interrupt Enable Read:
Register (KBIER) Write:
See page 100. Reset:
0
0
0
TBIF
$001C
Timebase Control Register Read:
(TBCR) Write:
See page 154.
Reset:
$0017
$0018
$0019
$001A
$001D
$001E
$001F
Register Name
IRQ Status and Control Read:
Register (ISCR) Write:
See page 94. Reset:
Configuration Register 2(1) Read:
(CONFIG2) Write:
See page 48. Reset:
Configuration Register 1(1) Read:
(CONFIG1) See page 47. Write:
POR Reset:
Other Resets:
Unaffected by reset
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
0
0
KEYF
0
IMASKK
MODEK
ACKK
0
0
0
0
0
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
TBIE
TBON
R
0
0
IMASK1
MODE1
0
0
TBR2
TBR1
TBR0
0
0
0
0
0
0
0
0
0
0
IRQF1
0
R
R
R
R
R
ACK1
0
0
0
0
0
0
0
0
0
EXTXTALEN
EXTSLOW
EXTCLKEN
0
OSCENINSTOP
SCIBDSRC
0
0
0
0
0
0
0
0
COPRS
LVISTOP
LVIRSTD
LVIPWRD
LVI5OR3
SSREC
STOP
COPD
0
0
0
0
0
0
0
0
0
U
0
0
0
0
0
0
PS1
PS0
R
TACK
1. LVI5OR3 is only writable after a power-on reset (POR). Bit 6 of CONFIG1 is read-only and will read 0.
All other bits in CONFIG1 and CONFIG2 are one-time writable after any reset.
TOF
$0020
Timer Status and Control Read:
Register (TSC) Write:
See page 163. Reset:
0
0
1
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
$0021
Timer Counter Register High Read:
(TCNTH) Write:
See page 164. Reset:
0
0
0
0
0
0
0
0
R
= Reserved
0
TOIE
TSTOP
= Unimplemented
0
0
TRST
PS2
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 5)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
26
Freescale Semiconductor
Monitor ROM
Addr.
$0022
$0023
$0024
Register Name
Timer Counter Register Low Read:
(TCNTL) Write:
See page 164. Reset:
Timer Counter Modulo Read:
Register High (TMODH) Write:
See page 165. Reset:
Timer Counter Modulo Read:
Register Low (TMODL) Write:
See page 165. Reset:
$0025
Timer Channel 0 Status and Read:
Control Register (TSC0) Write:
See page 165. Reset:
$0026
Timer Channel 0 Register Read:
High (TCH0H) Write:
See page 168. Reset:
$0027
$0028
Timer Channel 0 Register Read:
Low (TCH0L) Write:
See page 168. Reset:
Timer Channel 1 Status and Read:
Control Register (TSC1) Write:
See page 165. Reset:
$0029
Timer Channel 1 Register Read:
High (TCH1H) Write:
See page 168. Reset:
$002A
Timer Channel 1 Register Read:
Low (TCH1L) Write:
See page 168. Reset:
$002B
↓
$0035
$0036
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
1
1
1
1
1
1
1
1
Bit 7
6
5
4
3
2
1
Bit 0
1
1
1
1
1
1
1
1
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
CH0F
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH1F
0
0
CH1IE
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
Unimplemented
ICG Control Register Read:
(ICGCR) Write:
See page 87. Reset:
CMIE
0
CMF
ICGS
CS
ICGON
0
0
1
0
0
0
N6
N5
N4
N3
N2
N1
N0
0
0
1
0
1
0
1
R
= Reserved
0
ECGON
ECGS
CMON
0(1)
1. See 7.7.1 ICG Control Register for method of clearing the CMF bit.
$0037
ICG Multiplier Register Read:
(ICGMR) Write:
See page 88. Reset:
0
= Unimplemented
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 5)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
27
Memory
Addr.
$0038
$0039
$003A
Register Name
ICG Trim Register Read:
(ICGTR) Write:
See page 89. Reset:
ICG Divider Control Read:
Register (ICGDVR) Write:
See page 89. Reset:
ICG DCO Stage Control Read:
Register (ICGDSR) Write:
See page 89. Reset:
$003B
$003C
$003D
$003E
$003F
$FE00
Reserved
Analog-to-Digital Status and Read:
Control Register (ADSCR) Write:
See page 43. Reset:
Analog-to-Digital Data Read:
Register (ADR) Write:
See page 45. Reset:
Analog-to-Digital Input Clock Read:
Register (ADCLK) Write:
See page 45. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
TRIM7
TRIM6
TRIM5
TRIM4
TRIM3
TRIM2
TRIM1
TRIM0
1
0
0
0
0
0
0
0
DDIV3
DDIV2
DDIV1
DDIV0
0
0
0
0
U
U
U
U
DSTG7
DSTG6
DSTG5
DSTG4
DSTG3
DSTG2
DSTG1
DSTG0
R
R
R
R
R
R
R
R
U
U
U
U
U
U
U
U
R
R
R
R
R
R
R
R
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
0
0
1
1
1
1
1
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
R
R
R
R
R
R
R
R
0
0
0
COCO
R
Indeterminate after reset
ADIV2
ADIV1
ADIV0
ADICLK
R
0
0
0
0
0
0
0
0
0
0
0
1
0
0
BW
0
R
R
R
R
R
R
NOTE
R
0
0
0
1
0
0
0
0
POR
0
COP
ILOP
ILAD
MENRST
LVI
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
IF6
IF5
IF4
IF3
IF2
IF1
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
= Reserved
Unimplemented
SIM Break Status Register Read:
(SBSR)(1) Write:
See page 172. Reset:
1. Writing a 0 clears BW.
$FE01
SIM Reset Status Register Read:
(SRSR) Write:
See page 148. POR:
$FE02
Break Auxiliary Register Read:
(BRKAR) Write:
See page 173. Reset:
$FE03
SIM Break Flag Control Read:
Register (SBFCR) Write:
See page 173. Reset:
$FE04
Interrupt Status Register 1 Read:
(INT1) Write:
See page 149. Reset:
BDCOP
0
= Unimplemented
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 5)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
28
Freescale Semiconductor
Monitor ROM
Addr.
$FE05
$FE06
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Interrupt Status Register 2 Read:
(INT2) Write:
See page 150. Reset:
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Interrupt Status Register 3 Read:
(INT3) Write:
See page 150. Reset:
IF22
IF21
IF20
IF19
IF18
IF17
IF16
IF15
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
HVEN
MARGIN
ERASE
PGM
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
BRKE
BRKA
0
0
0
0
0
0
0
0
0
0
0
0
0
0
LVIOUT
0
0
0
0
0
0
R
0
0
0
0
0
0
0
0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
$FE07
Read:
FLASH Test Control
Write:
Register (FLTCR)
Reset:
$FE08
FLASH Control Register Read:
(FLCR) Write:
See page 31. Reset:
Break Address Register High Read:
$FE09
(BRKH) Write:
See page 172. Reset:
$FE0A
$FE0B
Break Address Register Low Read:
(BRKL) Write:
See page 172. Reset:
Break Status and Control Read:
Register (BRKSCR) Write:
See page 171. Reset:
$FE0C
Read:
LVI Status Register (LVISR)
Write:
See page 103.
Reset:
$FF7E
FLASH Block Protect Read:
Register (FLBPR)(1) Write:
See page 36. Reset:
Unaffected by reset
1. Non-volatile FLASH register
$FFFF
COP Control Register Read:
(COPCTL) Write:
See page 53. Reset:
Low byte of reset vector
Writing clears COP counter (any value)
Unaffected by reset
= Unimplemented
R
= Reserved
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 5)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
29
Memory
Table 2-1. Vector Locations
High
Priority
Low
Address
Vector
$FFDC
Timebase module vector (high)
$FFDD
Timebase module vector (low)
$FFDE
ADC conversion complete vector (high)
$FFDF
ADC conversion complete vector (low)
$FFE0
Keyboard vector (high)
$FFE1
Keyboard vector (low)
$FFE2
SCI transmit vector (high)
$FFE3
SCI transmit vector (low)
$FFE4
SCI receive vector (high)
$FFE5
SCI receive vector (low)
$FFE6
SCI receive error vector (high)
$FFE7
SCI receive error vector (low)
$FFE8
Reserved
$FFE9
Reserved
$FFEA
Reserved
$FFEB
Reserved
$FFEC
Reserved
$FFED
Reserved
$FFEE
Reserved
$FFEF
Reserved
$FFF0
Reserved
$FFF1
Reserved
$FFF2
TIM overflow vector (high)
$FFF3
TIM overflow vector (low)
$FFF4
TIM channel 1 vector (high)
$FFF5
TIM channel 1 vector (low)
$FFF6
TIM channel 0 vector (high)
$FFF7
TIM channel 0 vector (low)
$FFF8
CMIREQ vector (high)
$FFF9
CMIREQ vector (low)
$FFFA
IRQ1 vector (high)
$FFFB
IRQ1 vector (low)
$FFFC
SWI vector (high)
$FFFD
SWI vector (low)
$FFFE
Reset vector (high)
$FFFF
Reset vector (low)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
30
Freescale Semiconductor
Random-Access Memory (RAM)
2.4 Random-Access Memory (RAM)
Addresses $0040–$00FF are RAM locations. The location of the stack RAM is programmable. The 16-bit
stack pointer allows the stack to be anywhere in the 64-Kbyte memory space.
NOTE
For correct operation, the stack pointer must point only to RAM locations.
Before processing an interrupt, the CPU uses five bytes of the stack to save the contents of the CPU
registers.
NOTE
For M6805, M146805 and M68HC05compatibility, the H register is not
stacked.
During a subroutine call, the CPU uses two bytes of the stack to store the return address. The stack
pointer decrements during pushes and increments during pulls.
NOTE
Be careful when using nested subroutines. The CPU could overwrite data
in the RAM during a subroutine or during the interrupt stacking operation.
2.5 FLASH Memory (FLASH)
The FLASH memory is an array of 7,680 bytes with an additional 36 bytes of user vectors and one byte
used for block protection.
NOTE
An erased bit reads as 1 and a programmed bit reads as 0.
The program and erase operations are facilitated through control bits in the FLASH control register
(FLCR). See 2.6 FLASH Control Register.
The FLASH is organized internally as an 8192-word by 8-bit complementary metal-oxide semiconductor
(CMOS) page erase, byte (8-bit) program embedded FLASH memory. Each page consists of 64 bytes.
The page erase operation erases all words within a page. A page is composed of two adjacent rows.
A security feature prevents viewing of the FLASH contents.(1)
2.6 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase operations.
Address:
$FE08
Read:
Bit 7
6
5
4
0
0
0
0
0
0
0
Write:
Reset:
0
3
2
1
Bit 0
HVEN
MASS
ERASE
PGM
0
0
0
0
= Unimplemented
Figure 2-3. FLASH Control Register (FLCR)
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
31
Memory
HVEN — High-Voltage Enable Bit
This read/write bit enables the charge pump to drive high voltages for program and erase operations
in the array. HVEN can be set only if either PGM = 1 or ERASE = 1 and the proper sequence for
program or erase is followed.
1 = High voltage enabled to array and charge pump on
0 = High voltage disabled to array and charge pump off
MASS — Mass Erase Control Bit
Setting this read/write bit configures the 8-Kbyte FLASH array for mass erase operation.
1 = MASS erase operation selected
0 = MASS erase operation unselected
ERASE — Erase Control Bit
This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit
such that both bits cannot be equal to 1 or set to 1 at the same time.
1 = Erase operation selected
0 = Erase operation unselected
PGM — Program Control Bit
This read/write bit configures the memory for program operation. PGM is interlocked with the ERASE
bit such that both bits cannot be equal to 1 or set to 1 at the same time.
1 = Program operation selected
0 = Program operation unselected
2.7 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (64 bytes) of FLASH memory to read as 1:
1. Set the ERASE bit and clear the MASS bit in the FLASH control register.
2. Read the FLASH block protect register.
3. Write any data to any FLASH location within the address range of the block to be erased.
4. Wait for a time, tNVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tErase (minimum 1 ms or 4 ms).
7. Clear the ERASE bit.
8. Wait for a time, tNVH (minimum 5 µs).
9. Clear the HVEN bit.
10. After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
NOTE
While these operations must be performed in the order shown, other
unrelated operations may occur between the steps.
In applications that require more than 1000 program/erase cycles, use the 4 ms page erase specification
to get improved long-term reliability. Any application can use this 4 ms page erase specification. However,
in applications where a FLASH location will be erased and reprogrammed less than 1000 times, and
speed is important, use the 1 ms page erase specification to get a shorter cycle time.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
32
Freescale Semiconductor
FLASH Mass Erase Operation
2.8 FLASH Mass Erase Operation
Use the following procedure to erase the entire FLASH memory to read as a 1:
1. Set both the ERASE bit and the MASS bit in the FLASH control register.
2. Read the FLASH block protect register.
3. Write any data to any FLASH address(1) within the FLASH memory address range.
4. Wait for a time, tNVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tMErase (minimum 4 ms).
7. Clear the ERASE and MASS bits.
NOTE
Mass erase is disabled whenever any block is protected (FLBPR does not
equal $FF).
8. Wait for a time, tNVHL (minimum 100 µs).
9. Clear the HVEN bit.
10. After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps.
1. When in monitor mode, with security sequence failed (see 16.3.2 Security), write to the FLASH block protect register instead of any FLASH address.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
33
Memory
2.9 FLASH Program/Read Operation
Programming of the FLASH memory is done on a row basis. A row consists of 32 consecutive bytes
starting from addresses $XX00, $XX20, $XX40, $XX60, $XX80, $XXA0, $XXC0, and $XXE0. Use this
step-by-step procedure to program a row of FLASH memory (Figure 2-4 is a flowchart representation).
NOTE
Only bytes which are currently $FF may be programmed.
1. Set the PGM bit. This configures the memory for program operation and enables the latching of
address and data for programming.
2. Read the FLASH block protect register.
3. Write any data to any FLASH location within the address range desired.
4. Wait for a time, tNVS (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tPGS (minimum 5 µs).
7. Write data to the FLASH address being programmed(1).
8. Wait for time, tPROG (minimum 30 µs).
9. Repeat step 7 and 8 until all desired bytes within the row are programmed.
10. Clear the PGM bit(1).
11. Wait for time, tNVH (minimum 5 µs).
12. Clear the HVEN bit.
13. After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
This program sequence is repeated throughout the memory until all data is programmed.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps. Do not exceed tPROG maximum. See 17.11
Memory Characteristics.
1. The time between each FLASH address change, or the time between the last FLASH address programmed to clearing
PGM bit, must not exceed the maximum programming time, tPROG maximum.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
34
Freescale Semiconductor
FLASH Program/Read Operation
Algorithm for programming
a row (32 bytes) of FLASH memory
1
SET PGM BIT
2
READ THE FLASH BLOCK
PROTECT REGISTER
3
WRITE ANY DATA TO ANY FLASH ADDRESS
WITHIN THE ROW ADDRESS RANGE DESIRED
4
5
6
7
8
WAIT FOR A TIME, tNVS
SET HVEN BIT
WAIT FOR A TIME, tPGS
WRITE DATA TO THE FLASH ADDRESS
TO BE PROGRAMMED
WAIT FOR A TIME, tPROG
COMPLETED
PROGRAMMING
THIS ROW?
YES
NO
10
11
CLEAR PGM BIT
WAIT FOR A TIME, tNVH
Notes:
The time between each FLASH address change (step 7 to step 7),
or the time between the last FLASH address programmed
to clearing PGM bit (step 7 to step 10)
must not exceed the maximum programming
time, tPROG maximum.
12
13
This row program algorithm assumes the row/s
to be programmed are initially erased.
CLEAR HVEN BIT
WAIT FOR A TIME, tRCV
END OF PROGRAMMING
Figure 2-4. FLASH Programming Flowchart
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
35
Memory
2.10 FLASH Block Protection
Due to the ability of the on-board charge pump to erase and program the FLASH memory in the target
application, provision is made for protecting a block of memory from unintentional erase or program
operations due to system malfunction. This protection is done by using the FLASH block protect register
(FLBPR). The FLBPR determines the range of the FLASH memory which is to be protected. The range
of the protected area starts from a location defined by FLBPR and ends at the bottom of the FLASH
memory ($FFFF). When the memory is protected, the HVEN bit cannot be set in either erase or program
operations.
NOTE
In performing a program or erase operation, the FLASH block protect
register must be read after setting the PGM or ERASE bit and before
asserting the HVEN bit.
When FLBPR is programmed with all 0s, the entire memory is protected from being programmed and
erased. When all the bits are erased (all 1s), the entire memory is accessible for program and erase.
When bits within the FLBPR are programmed, they lock a block of memory address ranges as shown in
2.11 FLASH Block Protect Register. Once the FLBPR is programmed with a value other than $FF, any
erase or program of the FLBPR or the protected block of FLASH memory is prohibited. The FLBPR itself
can be erased or programmed only with an external voltage, VTST, present on the IRQ pin. This voltage
also allows entry from reset into the monitor mode.
2.11 FLASH Block Protect Register
The FLASH block protect register (FLBPR) is implemented as a byte within the FLASH memory, and
therefore can be written only during a programming sequence of the FLASH memory. The value in this
register determines the starting location of the protected range within the FLASH memory.
Address:
Read:
Write:
Reset:
$FF7E
Bit 7
6
5
4
3
2
1
Bit 0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
U
U
U
U
U
U
U
U
U = Unaffected by reset. Initial value from factory is 1.
Write to this register is by a programming sequence to the FLASH memory.
Figure 2-5. FLASH Block Protect Register (FLBPR)
BPR7–BPR0 — FLASH Block Protect Bits
These eight bits represent bits 13–6 of a 16-bit memory address. Bits 15 and 14 are 1s and bits 5–0
are 0s.
The resultant 16-bit address is used for specifying the start address of the FLASH memory for block
protection. The FLASH is protected from this start address to the end of FLASH memory, at $FFFF.
With this mechanism, the protect start address can be $XX00, $XX40, etc., (64 bytes page boundaries)
within the FLASH memory. See Figure 2-6 and Table 2-2.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
36
Freescale Semiconductor
Wait Mode
16-BIT MEMORY ADDRESS
START ADDRESS OF FLASH
BLOCK PROTECT
1
1
FLBPR VALUE
0
0
0
0
0
0
Figure 2-6. FLASH Block Protect Start Address
Table 2-2. Protect Start Address Examples
BPR7–BPR0
Start of Address of Protect Range(1)
$80
The entire FLASH memory is protected.
$81 (1000 0001)
$E040 (1110 0000 0100 0000)
$82 (1000 0010)
$E080 (1110 0000 1000 0000)
and so on...
$FE (1111 1110)
$FF80 (1111 1111 1000 0000)
$FF
The entire FLASH memory is not protected.
1. The end address of the protected range is always $FFFF.
2.12 Wait Mode
Putting the MCU into wait mode while the FLASH is in read mode does not affect the operation of the
FLASH memory directly, but there will not be any memory activity since the CPU is inactive.
The WAIT instruction should not be executed while performing a program or erase operation on the
FLASH, or the operation will discontinue and the FLASH will be on standby mode.
2.13 Stop Mode
Putting the MCU into stop mode while the FLASH is in read mode does not affect the operation of the
FLASH memory directly, but there will not be any memory activity since the CPU is inactive.
The STOP instruction should not be executed while performing a program or erase operation on the
FLASH, or the operation will discontinue and the FLASH will be on standby mode
NOTE
Standby mode is the power-saving mode of the FLASH module in which all
internal control signals to the FLASH are inactive and the current
consumption of the FLASH is at a minimum.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
37
Memory
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
38
Freescale Semiconductor
Chapter 3
Analog-to-Digital Converter (ADC)
3.1 Introduction
This section describes the 8-bit analog-to-digital converter (ADC).
3.2 Features
Features of the ADC module include:
• Four channels with multiplexed input
• Linear successive approximation
• 8-bit resolution
• Single or continuous conversion
• Conversion complete flag or conversion complete interrupt
• Selectable ADC clock
3.3 Functional Description
The ADC provides four pins for sampling external sources at pins PTB3–PTB0. An analog multiplexer
allows the single ADC converter to select one of four ADC channels as ADC voltage in (ADCVIN).
ADCVIN is converted by the successive approximation register-based counters. When the conversion is
completed, ADC places the result in the ADC data register and sets a flag or generates an interrupt. See
Figure 3-2.
The MC68HC908KX8 uses VDD as the high voltage reference.
3.3.1 ADC Port I/O Pins
PTB3–PTB0 are general-purpose input/output (I/O) pins that are shared with the ADC channels.
The channel select bits define which ADC channel/port pin will be used as the input signal. The ADC
overrides the port I/O logic by forcing that pin as input to the ADC. The remaining ADC channels/port pins
are controlled by the port I/O logic and can be used as general-purpose I/O. Writes to the port register or
DDR will not have any effect on the port pin that is selected by the ADC. Read of a port pin which is in
use by the ADC will return a logic 0 if the corresponding DDR bit is at 0. If the DDR bit is at 1, the value
in the port data latch is read.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
39
Freescale Semiconductor
SECURITY
MODULE
USER FLASH — 7680 BYTES
COMPUTER OPERATING PROPERLY
MODULE
LOW-VOLTAGE INHIBIT
MODULE
MONITOR ROM — 295 BYTES
2-CHANNEL TIMER INTERFACE
MODULE
USER FLASH VECTOR SPACE — 36 BYTES
FLASH BURN-IN ROM — 1024 BYTES
INTERNAL CLOCK GENERATOR
MODULE
(SOFTWARE SELECTABLE)
KEYBOARD INTERRUPT
MODULE
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATION INTERFACE
MODULE
SYSTEM INTEGRATION
MODULE
IRQ
MODULE
IRQ1(1)
VDD
VSS
PROGRAMMABLE TIME BASE
MODULE
BREAK
MODULE
POWER
Notes:
1. Pin contains integrated pullup resistor
2. High-current source/sink pin
3. Pin contains software selectable pullup resistor if general function I/O pin is configured as input.
Figure 3-1. Block Diagram Highlighting ADC Block and Pins
DDRA
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
PTA0/KBD0(2), (3)
PTA1/KBD1(2), (3)
PTA2/KBD2/TCH0(2), (3)
PTA3/KBD3/TCH1(2), (3)
PTA4/KBD4(2), (3)
POWER-ON RESET
MODULE
CONTROL AND STATUS REGISTERS — 78 BYTES
USER RAM — 192 BYTES
PTB
ARITHMETIC/LOGIC
UNIT
DDRB
CPU
REGISTERS
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
PTB5/TxD
PTB6/(OSC1)(4)
PTB7/(OSC2)/RST(4)
PTA
M68HC08 CPU
Analog-to-Digital Converter (ADC)
40
INTERNAL BUS
Functional Description
INTERNAL
DATA BUS
READ DDRB
WRITE
DISABLE
DDRBx
RESET
WRITE PTB
PTB
PTBx
ADC CHANNEL x
READ PTB
DISABLE
READ ADR
CONVERSION
COMPLETE
INTERRUPT
LOGIC
AIEN
ADC DATA REGISTER
ADC
BUS CLOCK
CHANNEL
SELECT
ADCH[4:0]
ADC CLOCK
COCO
CGMXCLK
ADC VOLTAGE IN
ADCVIN
CLOCK
GENERATOR
ADIV[2:0]
ADICLK
Figure 3-2. ADC Block Diagram
3.3.2 Voltage Conversion
When the input voltage to the ADC equals VREFH (see 17.9 Trimmed Accuracy of the Internal Clock
Generator), the ADC converts the signal to $FF (full scale). If the input voltage equals VSS, the ADC
converts it to $00. Input voltages between VREFH and VSS are a straight-line linear conversion. All other
input voltages will result in $FF if greater than VREFH and $00 if less than VSS.
NOTE
Input voltage should not exceed the high-voltage reference, which in turn
should not exceed supply voltages.
3.3.3 Conversion Time
Conversion starts after a write to the ADSCR (ADC status control register, $003C) and requires between
16 and 17 ADC clock cycles to complete. Conversion time in terms of the number of bus cycles is a
function of CGMXCLK frequency, bus frequency, the ADIV prescaler bits, and the ADICLK bit. For
example, with a CGMXCLK frequency of 8 MHz, bus frequency of 2 MHz, and fixed ADC clock frequency
of 1 MHz, one conversion will take between 16 and 17 µs and there will be 32 bus cycles between each
conversion. Sample rate is approximately 60 kHz.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
41
Analog-to-Digital Converter (ADC)
Refer to 17.9 Trimmed Accuracy of the Internal Clock Generator.
16 to 17 ADC clock cycles
Conversion time = ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯
ADC clock frequency
Number of bus cycles = conversion time x bus frequency
3.3.4 Continuous Conversion
In continuous conversion mode, the ADC data register will be filled with new data after each conversion.
Data from the previous conversion will be overwritten whether that data has been read or not.
Conversions will continue until the ADCO bit (ADC status control register, $003C) is cleared. The COCO
bit is set after the first conversion and will stay set until the next write of the ADC status and control register
or the next read of the ADC data register.
3.3.5 Accuracy and Precision
The conversion process is monotonic and has no missing codes. See 17.9 Trimmed Accuracy of the
Internal Clock Generator for accuracy information.
3.4 Interrupts
When the AIEN bit is set, the ADC module is capable of generating a CPU interrupt after each ADC
conversion. A CPU interrupt is generated if the COCO bit (ADC status control register, $003C) is at 0. If
the COCO bit is set, a direct-memory access (DMA) interrupt is generated.
NOTE
Because the MC68HC908KX8 does not have a DMA module, the COCO
bit should not be set while interrupts are enabled (AIEN = 1).
The COCO bit is not used as a conversion complete flag when interrupts are enabled.
3.5 Low-Power Modes
The following subsections describe the low-power modes.
3.5.1 Wait Mode
The ADC continues normal operation during wait mode. Any enabled CPU interrupt request from the ADC
can bring the MCU out of wait mode. If the ADC is not required to bring the MCU out of wait mode, power
down the ADC by setting the ADCH[4:0] bits in the ADC status and control register before executing the
WAIT instruction.
3.5.2 Stop Mode
The ADC module is inactive after the execution of a STOP instruction. Any pending conversion is aborted.
ADC conversions resume when the MCU exits stop mode. Allow one conversion cycle to stabilize the
analog circuitry before attempting a new ADC conversion after exiting stop mode.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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I/O Signals
3.6 I/O Signals
The ADC module has four channels that are shared with port B pins. Refer to 17.9 Trimmed Accuracy of
the Internal Clock Generator for voltages referenced here.
3.6.1 ADC Analog Power and ADC Voltage Reference Pins
The ADC analog portion uses VDD as its power pin and VSS as its ground pin.
Due to pin limitations, the VREFL signal is internally connected to VSS on the MC68HC908KX8. On the
MC68HC908KX8, the VREFH signal is internally connected to VDD.
3.6.2 ADC Voltage In (ADCVIN)
ADCVIN is the input voltage signal from one of the four ADC channels to the ADC module.
3.7 I/O Registers
These I/O registers control and monitor ADC operation:
• ADC status and control register, ADSCR
• ADC data register, ADR
• ADC clock register, ADICLK
3.7.1 ADC Status and Control Register
The following paragraphs describe the function of the ADC status and control register (ADSCR).
Address:
$003C
Bit 7
6
5
4
3
2
1
Bit 0
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
1
1
1
1
1
Read:
COCO
Write:
R
Reset:
0
0
R
= Reserved
Figure 3-3. ADC Status and Control Register (ADSCR)
COCO — Conversions Complete Bit
When the AIEN bit is a 0, the COCO is a read-only bit which is set each time a conversion is completed.
This bit is cleared whenever the ADC status and control register is written or whenever the ADC data
register is read.
When the AIEN bit is a 1, the ADC module is capable of generating a CPU interrupt after each ADC
conversion. A CPU interrupt is generated if the COCO bit (ADC status control register, $003C) is at 0.
If the COCO bit is at 1, a DMA interrupt is generated. Reset clears this bit.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0)
or CPU interrupts enabled (AIEN = 1)
NOTE
Because the MC68HC908KX8 does not have a DMA module, the COCO
bit should not be set while interrupts are enabled (AIEN = 1).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Analog-to-Digital Converter (ADC)
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is
cleared when the ADR register is read or the ADSCR register is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the ADR register at the end of each
conversion. Only one conversion is allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH4–ADCH0 — ADC Channel Select Bits
ADCH4–ADCH0 form a 5-bit field which is used to select the input for the A/D measurement.
The choices are one of four ADC channels, as well as VREFH and VSS. Input selection is detailed in
Table 3-1. Care should be taken when using a port pin as both an analog and a digital input
simultaneously to prevent switching noise from corrupting the analog signal.
The ADC subsystem is turned off when the channel select bits are all set to 1. This feature allows for
reduced power consumption for the MCU when the ADC is not used. Reset sets these bits.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
Table 3-1. Mux Channel Select
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
Input Select
0
0
0
0
0
PTB0
0
0
0
0
1
PTB1
0
0
0
1
0
PTB2
0
0
0
1
1
PTB3
0
0
1
0
0
Unused(1)
—
—
—
—
—
—
1
1
1
0
0
Unused (1)
1
1
1
0
1
VREFH(2)
1
1
1
1
0
VSSAD (2)
1
1
1
1
1
ADC power off
1. If any unused channels are selected, the resulting ADC conversion will be unknown.
2. The voltage levels supplied from internal reference nodes as specified in the table are used
to verify the operation of the ADC converter both in production test and for user applications.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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I/O Registers
3.7.2 ADC Data Register
One 8-bit result register is provided. This register is updated each time an ADC conversion completes.
Address:
$003D
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
Write:
R
R
R
R
R
R
R
R
Bit 0
Reset:
Indeterminate after reset
R
= Reserved
Figure 3-4. ADC Data Register (ADR)
3.7.3 ADC Input Clock Register
This register selects the clock frequency for the ADC.
Address:
$003E
Bit 7
Read:
Write:
Reset:
6
5
4
ADIV2
ADIV1
ADIV0
ADICLK
0
0
0
0
= Unimplemented
3
2
1
0
0
0
0
0
0
R
= Reserved
R
0
Figure 3-5. ADC Input Clock Register (ADICLK)
ADIV2–ADIV0 — ADC Clock Prescaler Bits
ADIV2, ADIV1, and ADIV0 form a 3-bit field which selects the divide ratio used by the ADC to generate
the internal ADC clock. Table 3-2 shows the available clock configurations. The ADC clock should be
set to approximately 1 MHz.
Table 3-2. ADC Clock Divide Ratio
ADIV2
ADIV1
ADIV0
ADC Clock Rate
0
0
0
ADC input clock ÷ 1
0
0
1
ADC input clock ÷ 2
0
1
0
ADC input clock ÷ 4
0
1
1
ADC input clock ÷ 8
1
X
X
ADC input clock ÷ 16
X = don’t care
ADICLK — ADC Input Clock Select Bit
ADICLK selects either bus clock or the oscillator output clock (CGMXCLK) as the input clock source
to generate the internal ADC rate clock. Reset selects CGMXCLK as the ADC clock source.
1 = Internal bus clock
0 = Oscillator output clock (CGMXCLK)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Analog-to-Digital Converter (ADC)
The ADC requires a clock rate of approximately 1 MHz for correct operation. If the selected clock
source is not fast enough, the ADC will generate incorrect conversions. See 17.9 Trimmed Accuracy
of the Internal Clock Generator.
fCGMXCLK or bus frequency
fADIC = ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ ≅ 1 MHz
ADIV[2:0]
NOTE
During the conversion process, changing the ADC clock will result in an
incorrect conversion.
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Chapter 4
Configuration Register (CONFIG)
4.1 Introduction
This section describes the configuration registers, CONFIG1 and CONFIG2. The configuration registers
control these options:
• Stop mode recovery time, 32 CGMXCLK cycles or 4096 CGMXCLK cycles
• Computer operating properly (COP) timeout period, 218–24 or 213–24 CGMXCLK cycles
• STOP instruction
• Computer operating properly (COP) module
• Low-voltage inhibit (LVI) module control and voltage trip point selection
• Enable/disable the oscillator (OSC) during stop mode
• Serial communications interface (SCI) clock source selection
• External clock/crystal source control
• Enable/disable for the FLASH charge-pump regulator
4.2 Functional Description
The configuration registers are used in the initialization of various options and can be written once after
each reset. All of the configuration register bits are cleared during reset. Since the various options affect
the operation of the microcontroller unit (MCU), it is recommended that these registers be written
immediately after reset. The configuration registers are located at $001E and $001F. For compatibility, a
write to a read-only memory (ROM) version of the MCU at this location will have no effect. The
configuration register may be read at anytime.
NOTE
The CONFIG module is known as an MOR (mask option register) on a
ROM device. On a ROM device, the options are fixed at the time of device
fabrication and are neither writable nor changeable by the user.
On a FLASH device, the CONFIG registers are special registers containing
one-time writable latches after each reset. Upon a reset, the CONFIG
registers default to predetermined settings as shown in Figure 4-1 and
Figure 4-2.
Address:
$001E
Bit 7
Read:
R
Write:
Reset:
0
6
5
4
3
2
1
Bit 0
0
EXTXTALEN
EXTSLOW
EXTCLKEN
0
OSCENINSTOP
SCIBDSRC
0
0
0
0
0
0
0
R
= Reserved
= Unimplemented
Figure 4-1. Configuration Register 2 (CONFIG2)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Configuration Register (CONFIG)
Address:
$001F
Bit 7
6
5
4
3
2
1
Bit 0
COPRS
LVISTOP
LVIRSTD
LVIPWRD
LVI5OR3(1)
SSREC
STOP
COPD
Reset:
0
0
0
0
0
0
0
0
Other Resets:
0
0
0
0
U
0
0
0
Read:
Write:
1. The LVI5OR3 bit is cleared only by a power-on reset (POR).
U = Unaffected
Figure 4-2. Configuration Register 1 (CONFIG1)
EXTCLKEN — External Clock Enable Bit
EXTCLKEN enables an external clock source or crystal/ceramic resonator to be used as a clock input.
Setting this bit enables PTB6/(OSC1) pin to be a clock input pin. Clearing this bit (default setting) allows
the PTB6/(OSC1) and PTB7/(OSC2)/RST pins to function as a general-purpose input/output (I/O) pin.
Refer to Table 4-1 for configuration options for the external source. See Chapter 7 Internal Clock
Generator Module (ICG) for a more detailed description of the external clock operation.
1 = Allows PTB6/(OSC1) to be an external clock connection
0 = PTB6/(OSC1) and PTB7/(OSC2)/RST function as I/O port pins (default).
Table 4-1. External Clock Option Settings
External Clock
Configuration Bits
Pin Function
Description
EXTCLKEN
EXTXTALEN
PTB6/(OSC1)
PTB7/(OSC2)/RST
0
0
PTB6
PTB7
Default setting — external oscillator disabled
0
1
PTB6
PTB7
External oscillator disabled since EXTCLKEN not set
1
0
OSC1
PTB7
External oscillator configured for an external clock
source input (square wave) on OSC1
1
1
OSC1
OSC2
External oscillator configured for an external crystal
configuration on OSC1 and OSC2. System will also
operate with square-wave clock source in OSC1.
EXTSLOW — Slow External Crystal Enable Bit
The EXTSLOW bit has two functions. It configures the ICG module for a fast (1 MHz to 8 MHz) or slow
(30 kHz to 100 kHz) speed crystal. The option also configures the clock monitor operation in the ICG
module to expect an external frequency higher (307.2 kHz to 32 MHz) or lower (60 Hz to 307.2 kHz)
than the base frequency of the internal oscillator. See Chapter 7 Internal Clock Generator Module
(ICG).
1 = ICG set for slow external crystal operation
0 = ICG set for fast external crystal operation
EXTXTALEN — External Crystal Enable Bit
EXTXTALEN enables the external oscillator circuits to be configured for a crystal configuration where
the PTB6/(OSC1) and PTB7/(OSC2)/RST pins are the connections for an external crystal.
NOTE
This bit does not function without setting the EXTCLKEN bit also.
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Functional Description
Clearing the EXTXTALEN bit (default setting) allows the PTB7/(OSC2)/RST pin to function as a
general-purpose I/O pin. Refer to Table 4-1 for configuration options for the external source. See
Chapter 7 Internal Clock Generator Module (ICG) for a more detailed description of the external clock
operation.
EXTXTALEN, when set, also configures the clock monitor to expect an external clock source in the
valid range of crystals (30 kHz to 100 kHz or 1 MHz to 8 MHz). When EXTXTALEN is clear, the clock
monitor will expect an external clock source in the valid range for externally generated clocks when
using the clock monitor (60 Hz to 32 MHz).
EXTXTALEN, when set, also configures the external clock stabilization divider in the clock monitor for
a 4096-cycle timeout to allow the proper stabilization time for a crystal. When EXTXTALEN is clear,
the stabilization divider is configured to 16 cycles since an external clock source does not need a
startup time.
1 = Allows PTB7/(OSC2)/RST to be an external crystal connection.
0 = PTB7/(OSC2)/RST functions as an I/O port pin (default).
OSCENINSTOP — Oscillator Enable In Stop Mode Bit
OSCENINSTOP, when set, will enable the internal clock generator module to continue to generate
clocks (either internal, ICLK, or external, ECLK) in stop mode. See Chapter 7 Internal Clock Generator
Module (ICG). This function is used to keep the timebase running while the rest of the microcontroller
stops. See Chapter 14 Timebase Module (TBM). When clear, all clock generation will cease and both
ICLK and ECLK will be forced low during stop mode. The default state for this option is clear, disabling
the ICG in stop mode.
1 = Oscillator enabled to operate during stop mode
0 = Oscillator disabled during stop mode (default)
NOTE
This bit has the same functionality as the OSCSTOPENB CONFIG bit in
MC68HC908GP20 and MC68HC908GR8 parts.
SCIBDSRC — SCI Baud Rate Clock Source Bit
SCIBDSRC controls the clock source used for the SCI. The setting of this bit affects the frequency at
which the SCI operates.
1 = Internal data bus clock is used as clock source for SCI.
0 = CGMXCLK is used as clock source for SCI.
COPRS — COP Rate Select Bit
COPD selects the COP timeout period. Reset clears COPRS. See Chapter 5 Computer Operating
Properly Module (COP).
1 = COP timeout period = 213 – 24 CGMXCLK cycles
0 = COP timeout period = 218 – 24 CGMXCLK cycles
LVISTOP — LVI Enable in Stop Mode Bit
When the LVIPWRD bit is clear, setting the LVISTOP bit enables the LVI to operate during stop mode.
Reset clears LVISTOP.
1 = LVI enabled during stop mode
0 = LVI disabled during stop mode
LVIRSTD — LVI Reset Disable Bit
LVIRSTD disables the reset signal from the LVI module. See Chapter 10 Low-Voltage Inhibit (LVI).
1 = LVI module resets disabled
0 = LVI module resets enabled
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Configuration Register (CONFIG)
LVIPWRD — LVI Power Disable Bit
LVIPWRD disables the LVI module. See Chapter 10 Low-Voltage Inhibit (LVI).
1 = LVI module power disabled
0 = LVI module power enabled
LVI5OR3 — LVI 5-V or 3-V Operating Mode Bit
LVI5OR3 selects the voltage operating mode of the LVI module (see See Chapter 10 Low-Voltage
Inhibit (LVI).). The voltage mode selected for the LVI should match the operating VDD. See Chapter 17
Electrical Specifications for the LVI’s voltage trip points for each of the modes.
1 = LVI operates in 5-V mode.
0 = LVI operates in 3-V mode.
NOTE
The LVI5OR3 bit is cleared by a power-on reset (POR) only. Other resets
will leave this bit unaffected.
SSREC — Short Stop Recovery Bit
SSREC enables the CPU to exit stop mode with a delay of 32 CGMXCLK cycles instead of a
4096-CGMXCLK cycle delay.
1 = Stop mode recovery after 32 CGMXCLK cycles
0 = Stop mode recovery after 4096 CGMXCLCK cycles
NOTE
Exiting stop mode by an LVI reset will result in the long stop recovery.
If the system clock source selected is the internal oscillator or the external crystal and the
OSCENINSTOP configuration bit is not set, the oscillator will be disabled during stop mode. The short
stop recovery does not provide enough time for oscillator stabilization and thus the SSREC bit should
not be set.
When using the LVI during normal operation but disabling during stop mode, the LVI will have an
enable time of tEN. The system stabilization time for power-on reset and long stop recovery (both 4096
CGMXCLK cycles) gives a delay longer than the LVI enable time for these startup scenarios. There is
no period where the MCU is not protected from a low-power condition. However, when using the short
stop recovery configuration option, the 32-CGMXCLK delay must be greater than the LVI’s turn on time
to avoid a period in startup where the LVI is not protecting the MCU.
STOP — STOP Instruction Enable Bit
STOP enables the STOP instruction.
1 = STOP instruction enabled
0 = STOP instruction treated as illegal opcode
COPD — COP Disable Bit
COPD disables the COP module. See Chapter 5 Computer Operating Properly Module (COP).
1 = COP module disabled
0 = COP module enabled
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Chapter 5
Computer Operating Properly Module (COP)
5.1 Introduction
The computer operating properly (COP) module contains a free-running counter that generates a reset if
allowed to overflow. The COP module helps software to recover from a runaway code. Periodically
clearing the COP counter will prevent a COP reset from occurring. The COP module can be disabled
through the COPD bit in the configuration (CONFIG) register.
5.2 Block Diagram
SIM MODULE
RESET VECTOR FETCH
RESET STATUS REGISTER
COP TIMEOUT
CLEAR STAGES 5–12
CLEAR ALL STAGES
INTERNAL RESET SOURCES(1)
SIM RESET CIRCUIT
12-BIT SIM COUNTER
BUSCLKX4
COPCTL WRITE
COP CLOCK
COP MODULE
6-BIT COP COUNTER
COPEN (FROM SIM)
COPD (FROM CONFIG1)
RESET
CLEAR
COP COUNTER
COPCTL WRITE
COP RATE SELECT
(COPRS FROM CONFIG1)
Figure 5-1. COP Block Diagram
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Computer Operating Properly Module (COP)
5.3 Functional Description
The COP counter is a free-running 6-bit counter preceded by a 12-bit prescaler. If not cleared by software,
the COP counter overflows and generates an asynchronous reset after 213–24 or 218–24 CGMXCLK
cycles, depending on the state of the COP rate select bit, COPRS, in the configuration register. With a
218–24 CGMXCLK cycle overflow option, a 4.9152-MHz CGMXCLK frequency gives a COP timeout
period of 53.3 ms. Writing any value to location $FFFF before an overflow occurs prevents a COP reset
by clearing the COP counter and stages 5–12 of the prescaler.
NOTE
Service the COP immediately after reset and before entering or after exiting
stop mode to guarantee the maximum time before the first COP counter
overflow.
A COP reset pulls an internal reset for 64 CGMXCLK cycles and sets the COP bit in the system integration
module (SIM) reset status register (SRSR).
In monitor mode, the COP is disabled if the IRQ1 pin is held at VTST.
NOTE
Place COP clearing instructions in the main program and not in an interrupt
subroutine. Such an interrupt subroutine could keep the COP from
generating a reset even while the main program is not working properly.
5.4 I/O Signals
The following paragraphs describe the signals shown in Figure 5-1.
5.4.1 CGMXCLK
CGMXCLK is the internal clock generator (ICG) module’s oscillator output signal. CGMXCLK is selected
from either the internal clock source or the external crystal.
5.4.2 STOP Instruction
The STOP instruction clears the COP prescaler.
5.4.3 COPCTL Write
Writing any value to the COP control register (COPCTL) clears the COP counter and clears stages 12–5
of the COP prescaler. Reading the COP control register returns the low byte of the reset vector.
5.4.4 Power-On Reset
The power-on reset (POR) circuit clears the COP prescaler 4096 CGMXCLK cycles after power-up.
5.4.5 Internal Reset
An internal reset clears the COP prescaler and the COP counter.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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COP Control Register
5.4.6 Reset Vector Fetch
A reset vector fetch occurs when the vector address appears on the data bus. A reset vector fetch clears
the COP prescaler.
5.4.7 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the configuration register. See
Chapter 4 Configuration Register (CONFIG).
5.4.8 COPRS (COP Rate Select)
The COPRS signal reflects the state of the COP rate select bit (COPRS) in the configuration register. See
Chapter 4 Configuration Register (CONFIG).
5.5 COP Control Register
The COP control register (COPCTL) is located at address $FFFF and overlaps the reset vector. Writing
any value to $FFFF clears the COP counter and stages 12–5 of the COP prescaler and starts a new
timeout period. Reading location $FFFF returns the low byte of the reset vector.
Address: $FFFF
Bit 7
6
5
4
3
Read:
Low byte of reset vector
Write:
Clear COP counter
Reset:
Unaffected by reset
2
1
Bit 0
Figure 5-2. COP Control Register (COPCTL)
5.6 Interrupts
The COP does not generate CPU interrupt requests.
5.7 Monitor Mode
The COP is disabled in monitor mode when VTST is present on the IRQ1 pin.
5.8 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
5.8.1 Wait Mode
The COP remains active in wait mode. To prevent a COP reset during wait mode, periodically clear the
COP counter in a CPU interrupt routine.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Computer Operating Properly Module (COP)
5.8.2 Stop Mode
Stop mode holds the 12-bit prescaler counter in reset until after stop mode is exited. Service the COP
immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering
or exiting stop mode.
To prevent inadvertently turning off the COP with a STOP instruction, a configuration option is available
that disables the STOP instruction. When the STOP bit in the configuration has the STOP instruction
disabled, execution of a STOP instruction results in an illegal opcode reset.
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Chapter 6
Central Processor Unit (CPU)
6.1 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully object-code-compatible version of
the M68HC05 CPU. The CPU08 Reference Manual (document order number CPU08RM/AD) contains a
description of the CPU instruction set, addressing modes, and architecture.
6.2 Features
Features of the CPU include:
• Object code fully upward-compatible with M68HC05 Family
• 16-bit stack pointer with stack manipulation instructions
• 16-bit index register with x-register manipulation instructions
• 8-MHz CPU internal bus frequency
• 64-Kbyte program/data memory space
• 16 addressing modes
• Memory-to-memory data moves without using accumulator
• Fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions
• Enhanced binary-coded decimal (BCD) data handling
• Modular architecture with expandable internal bus definition for extension of addressing range
beyond 64 Kbytes
• Low-power stop and wait modes
6.3 CPU Registers
Figure 6-1 shows the five CPU registers. CPU registers are not part of the memory map.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
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Central Processor Unit (CPU)
0
7
ACCUMULATOR (A)
0
15
H
X
INDEX REGISTER (H:X)
15
0
STACK POINTER (SP)
15
0
PROGRAM COUNTER (PC)
7
0
V 1 1 H I N Z C
CONDITION CODE REGISTER (CCR)
CARRY/BORROW FLAG
ZERO FLAG
NEGATIVE FLAG
INTERRUPT MASK
HALF-CARRY FLAG
TWO’S COMPLEMENT OVERFLOW FLAG
Figure 6-1. CPU Registers
6.3.1 Accumulator
The accumulator is a general-purpose 8-bit register. The CPU uses the accumulator to hold operands and
the results of arithmetic/logic operations.
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Unaffected by reset
Figure 6-2. Accumulator (A)
6.3.2 Index Register
The 16-bit index register allows indexed addressing of a 64-Kbyte memory space. H is the upper byte of
the index register, and X is the lower byte. H:X is the concatenated 16-bit index register.
In the indexed addressing modes, the CPU uses the contents of the index register to determine the
conditional address of the operand.
The index register can serve also as a temporary data storage location.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
0
0
0
0
0
0
0
0
X
X
X
X
X
X
X
X
Read:
Write:
Reset:
X = Indeterminate
Figure 6-3. Index Register (H:X)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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CPU Registers
6.3.3 Stack Pointer
The stack pointer is a 16-bit register that contains the address of the next location on the stack. During a
reset, the stack pointer is preset to $00FF. The reset stack pointer (RSP) instruction sets the least
significant byte to $FF and does not affect the most significant byte. The stack pointer decrements as data
is pushed onto the stack and increments as data is pulled from the stack.
In the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an
index register to access data on the stack. The CPU uses the contents of the stack pointer to determine
the conditional address of the operand.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Read:
Write:
Reset:
Figure 6-4. Stack Pointer (SP)
NOTE
The location of the stack is arbitrary and may be relocated anywhere in
random-access memory (RAM). Moving the SP out of page 0 ($0000 to
$00FF) frees direct address (page 0) space. For correct operation, the
stack pointer must point only to RAM locations.
6.3.4 Program Counter
The program counter is a 16-bit register that contains the address of the next instruction or operand to be
fetched.
Normally, the program counter automatically increments to the next sequential memory location every
time an instruction or operand is fetched. Jump, branch, and interrupt operations load the program
counter with an address other than that of the next sequential location.
During reset, the program counter is loaded with the reset vector address located at $FFFE and $FFFF.
The vector address is the address of the first instruction to be executed after exiting the reset state.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
Read:
Write:
Reset:
Loaded with vector from $FFFE and $FFFF
Figure 6-5. Program Counter (PC)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
57
Central Processor Unit (CPU)
6.3.5 Condition Code Register
The 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the
instruction just executed. Bits 6 and 5 are set permanently to 1. The following paragraphs describe the
functions of the condition code register.
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
V
1
1
H
I
N
Z
C
X
1
1
X
1
X
X
X
X = Indeterminate
Figure 6-6. Condition Code Register (CCR)
V — Overflow Flag
The CPU sets the overflow flag when a two's complement overflow occurs. The signed branch
instructions BGT, BGE, BLE, and BLT use the overflow flag.
1 = Overflow
0 = No overflow
H — Half-Carry Flag
The CPU sets the half-carry flag when a carry occurs between accumulator bits 3 and 4 during an
add-without-carry (ADD) or add-with-carry (ADC) operation. The half-carry flag is required for
binary-coded decimal (BCD) arithmetic operations. The DAA instruction uses the states of the H and
C flags to determine the appropriate correction factor.
1 = Carry between bits 3 and 4
0 = No carry between bits 3 and 4
I — Interrupt Mask
When the interrupt mask is set, all maskable CPU interrupts are disabled. CPU interrupts are enabled
when the interrupt mask is cleared. When a CPU interrupt occurs, the interrupt mask is set
automatically after the CPU registers are saved on the stack, but before the interrupt vector is fetched.
1 = Interrupts disabled
0 = Interrupts enabled
NOTE
To maintain M6805 Family compatibility, the upper byte of the index
register (H) is not stacked automatically. If the interrupt service routine
modifies H, then the user must stack and unstack H using the PSHH and
PULH instructions.
After the I bit is cleared, the highest-priority interrupt request is serviced first.
A return-from-interrupt (RTI) instruction pulls the CPU registers from the stack and restores the
interrupt mask from the stack. After any reset, the interrupt mask is set and can be cleared only by the
clear interrupt mask software instruction (CLI).
N — Negative Flag
The CPU sets the negative flag when an arithmetic operation, logic operation, or data manipulation
produces a negative result, setting bit 7 of the result.
1 = Negative result
0 = Non-negative result
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
58
Freescale Semiconductor
Arithmetic/Logic Unit (ALU)
Z — Zero Flag
The CPU sets the zero flag when an arithmetic operation, logic operation, or data manipulation
produces a result of $00.
1 = Zero result
0 = Non-zero result
C — Carry/Borrow Flag
The CPU sets the carry/borrow flag when an addition operation produces a carry out of bit 7 of the
accumulator or when a subtraction operation requires a borrow. Some instructions — such as bit test
and branch, shift, and rotate — also clear or set the carry/borrow flag.
1 = Carry out of bit 7
0 = No carry out of bit 7
6.4 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the instruction set.
Refer to the CPU08 Reference Manual (document order number CPU08RM/AD) for a description of the
instructions and addressing modes and more detail about the architecture of the CPU.
6.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
6.5.1 Wait Mode
The WAIT instruction:
• Clears the interrupt mask (I bit) in the condition code register, enabling interrupts. After exit from
wait mode by interrupt, the I bit remains clear. After exit by reset, the I bit is set.
• Disables the CPU clock
6.5.2 Stop Mode
The STOP instruction:
• Clears the interrupt mask (I bit) in the condition code register, enabling external interrupts. After
exit from stop mode by external interrupt, the I bit remains clear. After exit by reset, the I bit is set.
• Disables the CPU clock
After exiting stop mode, the CPU clock begins running after the oscillator stabilization delay.
6.6 CPU During Break Interrupts
If a break module is present on the MCU, the CPU starts a break interrupt by:
• Loading the instruction register with the SWI instruction
• Loading the program counter with $FFFC:$FFFD or with $FEFC:$FEFD in monitor mode
The break interrupt begins after completion of the CPU instruction in progress. If the break address
register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately.
A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and returns the MCU
to normal operation if the break interrupt has been deasserted.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
59
Central Processor Unit (CPU)
6.7 Instruction Set Summary
Table 6-1 provides a summary of the M68HC08 instruction set.
ADC #opr
ADC opr
ADC opr
ADC opr,X
ADC opr,X
ADC ,X
ADC opr,SP
ADC opr,SP
ADD #opr
ADD opr
ADD opr
ADD opr,X
ADD opr,X
ADD ,X
ADD opr,SP
ADD opr,SP
V H I N Z C
A ← (A) + (M) + (C)
Add with Carry
A ← (A) + (M)
Add without Carry
IMM
DIR
EXT
IX2
– IX1
IX
SP1
SP2
A9
B9
C9
D9
E9
F9
9EE9
9ED9
ii
dd
hh ll
ee ff
ff
IMM
DIR
EXT
– IX2
IX1
IX
SP1
SP2
AB
BB
CB
DB
EB
FB
9EEB
9EDB
ii
dd
hh ll
ee ff
ff
ff
ee ff
Cycles
Effect
on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 1 of 6)
2
3
4
4
3
2
4
5
ff
ee ff
2
3
4
4
3
2
4
5
AIS #opr
Add Immediate Value (Signed) to SP
SP ← (SP) + (16 « M)
– – – – – – IMM
A7
ii
2
AIX #opr
Add Immediate Value (Signed) to H:X
H:X ← (H:X) + (16 « M)
– – – – – – IMM
AF
ii
2
A ← (A) & (M)
IMM
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
A4
B4
C4
D4
E4
F4
9EE4
9ED4
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
0
DIR
INH
INH
– – IX1
IX
SP1
38 dd
48
58
68 ff
78
9E68 ff
4
1
1
4
3
5
C
DIR
INH
– – INH
IX1
IX
SP1
37 dd
47
57
67 ff
77
9E67 ff
4
1
1
4
3
5
AND #opr
AND opr
AND opr
AND opr,X
AND opr,X
AND ,X
AND opr,SP
AND opr,SP
ASL opr
ASLA
ASLX
ASL opr,X
ASL ,X
ASL opr,SP
Logical AND
Arithmetic Shift Left
(Same as LSL)
C
b7
ASR opr
ASRA
ASRX
ASR opr,X
ASR opr,X
ASR opr,SP
Arithmetic Shift Right
BCC rel
Branch if Carry Bit Clear
b0
b7
BCLR n, opr
Clear Bit n in M
b0
PC ← (PC) + 2 + rel ? (C) = 0
Mn ← 0
ff
ee ff
– – – – – – REL
24
rr
3
DIR (b0)
DIR (b1)
DIR (b2)
– – – – – – DIR (b3)
DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
11
13
15
17
19
1B
1D
1F
dd
dd
dd
dd
dd
dd
dd
dd
4
4
4
4
4
4
4
4
BCS rel
Branch if Carry Bit Set (Same as BLO)
PC ← (PC) + 2 + rel ? (C) = 1
– – – – – – REL
25
rr
3
BEQ rel
Branch if Equal
PC ← (PC) + 2 + rel ? (Z) = 1
– – – – – – REL
27
rr
3
BGE opr
Branch if Greater Than or Equal To
(Signed Operands)
PC ← (PC) + 2 + rel ? (N ⊕ V) = 0
– – – – – – REL
90
rr
3
BGT opr
Branch if Greater Than (Signed
Operands)
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 0 – – – – – – REL
92
rr
3
BHCC rel
Branch if Half Carry Bit Clear
PC ← (PC) + 2 + rel ? (H) = 0
– – – – – – REL
28
rr
BHCS rel
Branch if Half Carry Bit Set
PC ← (PC) + 2 + rel ? (H) = 1
– – – – – – REL
29
rr
BHI rel
Branch if Higher
PC ← (PC) + 2 + rel ? (C) | (Z) = 0
– – – – – – REL
22
rr
3
3
3
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
60
Freescale Semiconductor
Instruction Set Summary
Effect
on CCR
V H I N Z C
BHS rel
Branch if Higher or Same
(Same as BCC)
BIH rel
BIL rel
PC ← (PC) + 2 + rel ? (C) = 0
– – – – – – REL
Branch if IRQ Pin High
PC ← (PC) + 2 + rel ? IRQ = 1
Branch if IRQ Pin Low
PC ← (PC) + 2 + rel ? IRQ = 0
(A) & (M)
BIT #opr
BIT opr
BIT opr
BIT opr,X
BIT opr,X
BIT ,X
BIT opr,SP
BIT opr,SP
Bit Test
BLE opr
Branch if Less Than or Equal To
(Signed Operands)
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 2 of 6)
24
rr
3
– – – – – – REL
2F
rr
3
– – – – – – REL
2E
rr
3
IMM
DIR
EXT
0 – – – IX2
IX1
IX
SP1
SP2
A5
B5
C5
D5
E5
F5
9EE5
9ED5
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
rr
3
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 1 – – – – – – REL
93
BLO rel
Branch if Lower (Same as BCS)
PC ← (PC) + 2 + rel ? (C) = 1
– – – – – – REL
25
rr
3
BLS rel
Branch if Lower or Same
PC ← (PC) + 2 + rel ? (C) | (Z) = 1
– – – – – – REL
23
rr
3
BLT opr
Branch if Less Than (Signed Operands)
PC ← (PC) + 2 + rel ? (N ⊕ V) =1
– – – – – – REL
91
rr
3
BMC rel
Branch if Interrupt Mask Clear
PC ← (PC) + 2 + rel ? (I) = 0
– – – – – – REL
2C
rr
3
BMI rel
Branch if Minus
PC ← (PC) + 2 + rel ? (N) = 1
– – – – – – REL
2B
rr
3
BMS rel
Branch if Interrupt Mask Set
PC ← (PC) + 2 + rel ? (I) = 1
– – – – – – REL
2D
rr
3
3
BNE rel
Branch if Not Equal
PC ← (PC) + 2 + rel ? (Z) = 0
– – – – – – REL
26
rr
BPL rel
Branch if Plus
PC ← (PC) + 2 + rel ? (N) = 0
– – – – – – REL
2A
rr
3
BRA rel
Branch Always
PC ← (PC) + 2 + rel
– – – – – – REL
20
rr
3
DIR (b0)
DIR (b1)
DIR (b2)
DIR (b3)
– – – – – DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
01
03
05
07
09
0B
0D
0F
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
5
5
5
5
5
5
5
5
BRCLR n,opr,rel Branch if Bit n in M Clear
BRN rel
Branch Never
BRSET n,opr,rel Branch if Bit n in M Set
BSET n,opr
Set Bit n in M
BSR rel
Branch to Subroutine
CBEQ opr,rel
CBEQA #opr,rel
CBEQX #opr,rel Compare and Branch if Equal
CBEQ opr,X+,rel
CBEQ X+,rel
CBEQ opr,SP,rel
PC ← (PC) + 3 + rel ? (Mn) = 0
PC ← (PC) + 2
– – – – – – REL
21
rr
3
PC ← (PC) + 3 + rel ? (Mn) = 1
DIR (b0)
DIR (b1)
DIR (b2)
DIR (b3)
– – – – – DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
00
02
04
06
08
0A
0C
0E
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
5
5
5
5
5
5
5
5
Mn ← 1
DIR (b0)
DIR (b1)
DIR (b2)
– – – – – – DIR (b3)
DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
10
12
14
16
18
1A
1C
1E
dd
dd
dd
dd
dd
dd
dd
dd
4
4
4
4
4
4
4
4
PC ← (PC) + 2; push (PCL)
SP ← (SP) – 1; push (PCH)
SP ← (SP) – 1
PC ← (PC) + rel
– – – – – – REL
AD
rr
4
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (X) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 2 + rel ? (A) – (M) = $00
PC ← (PC) + 4 + rel ? (A) – (M) = $00
DIR
IMM
– – – – – – IMM
IX1+
IX+
SP1
31
41
51
61
71
9E61
dd rr
ii rr
ii rr
ff rr
rr
ff rr
5
4
4
5
4
6
CLC
Clear Carry Bit
C←0
– – – – – 0 INH
98
1
CLI
Clear Interrupt Mask
I←0
– – 0 – – – INH
9A
2
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
61
Central Processor Unit (CPU)
CLR opr
CLRA
CLRX
CLRH
CLR opr,X
CLR ,X
CLR opr,SP
CMP #opr
CMP opr
CMP opr
CMP opr,X
CMP opr,X
CMP ,X
CMP opr,SP
CMP opr,SP
Clear
Compare A with M
Complement (One’s Complement)
CPHX #opr
CPHX opr
Compare H:X with M
CPX #opr
CPX opr
CPX opr
CPX ,X
CPX opr,X
CPX opr,X
CPX opr,SP
CPX opr,SP
Compare X with M
DAA
Decimal Adjust A
DBNZ opr,rel
DBNZA rel
DBNZX rel
Decrement and Branch if Not Zero
DBNZ opr,X,rel
DBNZ X,rel
DBNZ opr,SP,rel
DEC opr
DECA
DECX
DEC opr,X
DEC ,X
DEC opr,SP
Decrement
DIV
Divide
INC opr
INCA
INCX
INC opr,X
INC ,X
INC opr,SP
Exclusive OR M with A
Increment
M ← $00
A ← $00
X ← $00
H ← $00
M ← $00
M ← $00
M ← $00
DIR
INH
INH
0 – – 0 1 – INH
IX1
IX
SP1
3F dd
4F
5F
8C
6F ff
7F
9E6F ff
(A) – (M)
IMM
DIR
EXT
IX2
– – IX1
IX
SP1
SP2
A1
B1
C1
D1
E1
F1
9EE1
9ED1
DIR
INH
INH
0 – – 1
IX1
IX
SP1
33 dd
43
53
63 ff
73
9E63 ff
M ← (M) = $FF – (M)
A ← (A) = $FF – (M)
X ← (X) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
(H:X) – (M:M + 1)
(X) – (M)
(A)10
IMM
DIR
ii
dd
hh ll
ee ff
ff
ff
ee ff
3
1
1
1
3
2
4
2
3
4
4
3
2
4
5
4
1
1
4
3
5
65
75
ii ii+1
dd
3
4
IMM
DIR
EXT
IX2
– – IX1
IX
SP1
SP2
A3
B3
C3
D3
E3
F3
9EE3
9ED3
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
U – – INH
72
– – A ← (A) – 1 or M ← (M) – 1 or X ← (X) – 1
PC ← (PC) + 3 + rel ? (result) ≠ 0
DIR
PC ← (PC) + 2 + rel ? (result) ≠ 0
INH
PC ← (PC) + 2 + rel ? (result) ≠ 0
– – – – – – INH
PC ← (PC) + 3 + rel ? (result) ≠ 0
IX1
PC ← (PC) + 2 + rel ? (result) ≠ 0
IX
PC ← (PC) + 4 + rel ? (result) ≠ 0
SP1
3B
4B
5B
6B
7B
9E6B
ff
ee ff
2
dd rr
rr
rr
ff rr
rr
ff rr
M ← (M) – 1
A ← (A) – 1
X ← (X) – 1
M ← (M) – 1
M ← (M) – 1
M ← (M) – 1
DIR
INH
INH
– – –
IX1
IX
SP1
A ← (H:A)/(X)
H ← Remainder
– – – – INH
52
A ← (A ⊕ M)
IMM
DIR
EXT
0 – – – IX2
IX1
IX
SP1
SP2
A8
B8
C8
D8
E8
F8
9EE8
9ED8
DIR
INH
– – – INH
IX1
IX
SP1
3C dd
4C
5C
6C ff
7C
9E6C ff
M ← (M) + 1
A ← (A) + 1
X ← (X) + 1
M ← (M) + 1
M ← (M) + 1
M ← (M) + 1
Cycles
Effect
on CCR
V H I N Z C
COM opr
COMA
COMX
COM opr,X
COM ,X
COM opr,SP
EOR #opr
EOR opr
EOR opr
EOR opr,X
EOR opr,X
EOR ,X
EOR opr,SP
EOR opr,SP
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 3 of 6)
3A dd
4A
5A
6A ff
7A
9E6A ff
5
3
3
5
4
6
4
1
1
4
3
5
7
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
4
1
1
4
3
5
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
62
Freescale Semiconductor
Instruction Set Summary
JSR opr
JSR opr
JSR opr,X
JSR opr,X
JSR ,X
Jump to Subroutine
LDHX #opr
LDHX opr
Load H:X from M
2
3
4
3
2
PC ← (PC) + n (n = 1, 2, or 3)
Push (PCL); SP ← (SP) – 1
Push (PCH); SP ← (SP) – 1
PC ← Unconditional Address
DIR
EXT
– – – – – – IX2
IX1
IX
BD
CD
DD
ED
FD
dd
hh ll
ee ff
ff
4
5
6
5
4
A ← (M)
IMM
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
A6
B6
C6
D6
E6
F6
9EE6
9ED6
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
ii jj
dd
3
4
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
H:X ← (M:M + 1)
Logical Shift Left
(Same as ASL)
Logical Shift Right
MOV opr,opr
MOV opr,X+
MOV #opr,opr
MOV X+,opr
Move
MUL
Unsigned multiply
0 – – –
b7
AE
BE
CE
DE
EE
FE
9EEE
9EDE
0
DIR
INH
INH
– – IX1
IX
SP1
38 dd
48
58
68 ff
78
9E68 ff
4
1
1
4
3
5
C
DIR
INH
– – 0 INH
IX1
IX
SP1
34 dd
44
54
64 ff
74
9E64 ff
4
1
1
4
3
5
b0
0
b7
b0
H:X ← (H:X) + 1 (IX+D, DIX+)
DD
DIX+
0 – – – IMD
IX+D
X:A ← (X) × (A)
– 0 – – – 0 INH
M ← –(M) = $00 – (M)
A ← –(A) = $00 – (A)
X ← –(X) = $00 – (X)
M ← –(M) = $00 – (M)
M ← –(M) = $00 – (M)
DIR
INH
INH
– – IX1
IX
SP1
(M)Destination ← (M)Source
Negate (Two’s Complement)
45
55
IMM
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
X ← (M)
C
IMM
DIR
4E
5E
6E
7E
dd dd
dd
ii dd
dd
42
No Operation
None
– – – – – – INH
9D
NSA
Nibble Swap A
A ← (A[3:0]:A[7:4])
– – – – – – INH
62
A ← (A) | (M)
IMM
DIR
EXT
IX2
0 – – –
IX1
IX
SP1
SP2
AA
BA
CA
DA
EA
FA
9EEA
9EDA
Inclusive OR A and M
ff
ee ff
5
4
4
4
5
30 dd
40
50
60 ff
70
9E60 ff
NOP
ORA #opr
ORA opr
ORA opr
ORA opr,X
ORA opr,X
ORA ,X
ORA opr,SP
ORA opr,SP
Cycles
dd
hh ll
ee ff
ff
Load X from M
LSR opr
LSRA
LSRX
LSR opr,X
LSR ,X
LSR opr,SP
NEG opr
NEGA
NEGX
NEG opr,X
NEG ,X
NEG opr,SP
BC
CC
DC
EC
FC
Jump
Load A from M
LSL opr
LSLA
LSLX
LSL opr,X
LSL ,X
LSL opr,SP
PC ← Jump Address
DIR
EXT
– – – – – – IX2
IX1
IX
Effect
on CCR
Description
V H I N Z C
LDA #opr
LDA opr
LDA opr
LDA opr,X
LDA opr,X
LDA ,X
LDA opr,SP
LDA opr,SP
LDX #opr
LDX opr
LDX opr
LDX opr,X
LDX opr,X
LDX ,X
LDX opr,SP
LDX opr,SP
Operand
JMP opr
JMP opr
JMP opr,X
JMP opr,X
JMP ,X
Operation
Address
Mode
Source
Form
Opcode
Table 6-1. Instruction Set Summary (Sheet 4 of 6)
4
1
1
4
3
5
1
3
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
PSHA
Push A onto Stack
Push (A); SP ← (SP) – 1
– – – – – – INH
87
2
PSHH
Push H onto Stack
Push (H); SP ← (SP) – 1
– – – – – – INH
8B
2
PSHX
Push X onto Stack
Push (X); SP ← (SP) – 1
– – – – – – INH
89
2
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
63
Central Processor Unit (CPU)
V H I N Z C
Cycles
Effect
on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 5 of 6)
PULA
Pull A from Stack
SP ← (SP + 1); Pull (A)
– – – – – – INH
86
2
PULH
Pull H from Stack
SP ← (SP + 1); Pull (H)
– – – – – – INH
8A
2
PULX
Pull X from Stack
SP ← (SP + 1); Pull (X)
– – – – – – INH
C
DIR
INH
INH
– – IX1
IX
SP1
39 dd
49
59
69 ff
79
9E69 ff
4
1
1
4
3
5
DIR
INH
– – INH
IX1
IX
SP1
36 dd
46
56
66 ff
76
9E66 ff
4
1
1
4
3
5
ROL opr
ROLA
ROLX
ROL opr,X
ROL ,X
ROL opr,SP
Rotate Left through Carry
b7
b0
88
2
ROR opr
RORA
RORX
ROR opr,X
ROR ,X
ROR opr,SP
Rotate Right through Carry
RSP
Reset Stack Pointer
SP ← $FF
– – – – – – INH
9C
1
RTI
Return from Interrupt
SP ← (SP) + 1; Pull (CCR)
SP ← (SP) + 1; Pull (A)
SP ← (SP) + 1; Pull (X)
SP ← (SP) + 1; Pull (PCH)
SP ← (SP) + 1; Pull (PCL)
INH
80
7
RTS
Return from Subroutine
SP ← SP + 1; Pull (PCH)
SP ← SP + 1; Pull (PCL)
– – – – – – INH
81
4
A ← (A) – (M) – (C)
IMM
DIR
EXT
– – IX2
IX1
IX
SP1
SP2
A2
B2
C2
D2
E2
F2
9EE2
9ED2
SBC #opr
SBC opr
SBC opr
SBC opr,X
SBC opr,X
SBC ,X
SBC opr,SP
SBC opr,SP
C
b7
Subtract with Carry
b0
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
SEC
Set Carry Bit
C←1
– – – – – 1 INH
99
1
SEI
Set Interrupt Mask
I←1
– – 1 – – – INH
9B
2
M ← (A)
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
B7
C7
D7
E7
F7
9EE7
9ED7
(M:M + 1) ← (H:X)
0 – – – DIR
35
I ← 0; Stop Processing
– – 0 – – – INH
8E
M ← (X)
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
BF
CF
DF
EF
FF
9EEF
9EDF
dd
hh ll
ee ff
ff
IMM
DIR
EXT
– – IX2
IX1
IX
SP1
SP2
A0
B0
C0
D0
E0
F0
9EE0
9ED0
ii
dd
hh ll
ee ff
ff
STA opr
STA opr
STA opr,X
STA opr,X
STA ,X
STA opr,SP
STA opr,SP
Store A in M
STHX opr
Store H:X in M
STOP
Enable Interrupts, Stop Processing,
Refer to MCU Documentation
STX opr
STX opr
STX opr,X
STX opr,X
STX ,X
STX opr,SP
STX opr,SP
SUB #opr
SUB opr
SUB opr
SUB opr,X
SUB opr,X
SUB ,X
SUB opr,SP
SUB opr,SP
Store X in M
Subtract
A ← (A) – (M)
dd
hh ll
ee ff
ff
ff
ee ff
3
4
4
3
2
4
5
dd
4
1
ff
ee ff
ff
ee ff
3
4
4
3
2
4
5
2
3
4
4
3
2
4
5
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
64
Freescale Semiconductor
Opcode Map
SWI
Software Interrupt
PC ← (PC) + 1; Push (PCL)
SP ← (SP) – 1; Push (PCH)
SP ← (SP) – 1; Push (X)
SP ← (SP) – 1; Push (A)
SP ← (SP) – 1; Push (CCR)
SP ← (SP) – 1; I ← 1
PCH ← Interrupt Vector High Byte
PCL ← Interrupt Vector Low Byte
– – 1 – – – INH
83
9
CCR ← (A)
INH
84
2
X ← (A)
– – – – – – INH
97
1
A ← (CCR)
– – – – – – INH
85
(A) – $00 or (X) – $00 or (M) – $00
DIR
INH
INH
0 – – –
IX1
IX
SP1
H:X ← (SP) + 1
– – – – – – INH
95
2
A ← (X)
– – – – – – INH
9F
1
(SP) ← (H:X) – 1
– – – – – – INH
94
2
I bit ← 0; Inhibit CPU clocking
until interrupted
– – 0 – – – INH
8F
1
TAP
Transfer A to CCR
Transfer A to X
TPA
Transfer CCR to A
Test for Negative or Zero
TSX
Transfer SP to H:X
TXA
Transfer X to A
TXS
Transfer H:X to SP
WAIT
A
C
CCR
dd
dd rr
DD
DIR
DIX+
ee ff
EXT
ff
H
H
hh ll
I
ii
IMD
IMM
INH
IX
IX+
IX+D
IX1
IX1+
IX2
M
N
Cycles
V H I N Z C
TAX
TST opr
TSTA
TSTX
TST opr,X
TST ,X
TST opr,SP
Effect
on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 6 of 6)
Enable Interrupts; Wait for Interrupt
Accumulator
Carry/borrow bit
Condition code register
Direct address of operand
Direct address of operand and relative offset of branch instruction
Direct to direct addressing mode
Direct addressing mode
Direct to indexed with post increment addressing mode
High and low bytes of offset in indexed, 16-bit offset addressing
Extended addressing mode
Offset byte in indexed, 8-bit offset addressing
Half-carry bit
Index register high byte
High and low bytes of operand address in extended addressing
Interrupt mask
Immediate operand byte
Immediate source to direct destination addressing mode
Immediate addressing mode
Inherent addressing mode
Indexed, no offset addressing mode
Indexed, no offset, post increment addressing mode
Indexed with post increment to direct addressing mode
Indexed, 8-bit offset addressing mode
Indexed, 8-bit offset, post increment addressing mode
Indexed, 16-bit offset addressing mode
Memory location
Negative bit
n
opr
PC
PCH
PCL
REL
rel
rr
SP1
SP2
SP
U
V
X
Z
&
|
⊕
()
–( )
#
«
←
?
:
—
3D dd
4D
5D
6D ff
7D
9E6D ff
1
3
1
1
3
2
4
Any bit
Operand (one or two bytes)
Program counter
Program counter high byte
Program counter low byte
Relative addressing mode
Relative program counter offset byte
Relative program counter offset byte
Stack pointer, 8-bit offset addressing mode
Stack pointer 16-bit offset addressing mode
Stack pointer
Undefined
Overflow bit
Index register low byte
Zero bit
Logical AND
Logical OR
Logical EXCLUSIVE OR
Contents of
Negation (two’s complement)
Immediate value
Sign extend
Loaded with
If
Concatenated with
Set or cleared
Not affected
6.8 Opcode Map
See Table 6-2.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
65
MSB
Branch
REL
DIR
INH
3
4
0
1
2
5
BRSET0
3 DIR
5
BRCLR0
3 DIR
5
BRSET1
3 DIR
5
BRCLR1
3 DIR
5
BRSET2
3 DIR
5
BRCLR2
3 DIR
5
BRSET3
3 DIR
5
BRCLR3
3 DIR
5
BRSET4
3 DIR
5
BRCLR4
3 DIR
5
BRSET5
3 DIR
5
BRCLR5
3 DIR
5
BRSET6
3 DIR
5
BRCLR6
3 DIR
5
BRSET7
3 DIR
5
BRCLR7
3 DIR
4
BSET0
2 DIR
4
BCLR0
2 DIR
4
BSET1
2 DIR
4
BCLR1
2 DIR
4
BSET2
2 DIR
4
BCLR2
2 DIR
4
BSET3
2 DIR
4
BCLR3
2 DIR
4
BSET4
2 DIR
4
BCLR4
2 DIR
4
BSET5
2 DIR
4
BCLR5
2 DIR
4
BSET6
2 DIR
4
BCLR6
2 DIR
4
BSET7
2 DIR
4
BCLR7
2 DIR
3
BRA
2 REL
3
BRN
2 REL
3
BHI
2 REL
3
BLS
2 REL
3
BCC
2 REL
3
BCS
2 REL
3
BNE
2 REL
3
BEQ
2 REL
3
BHCC
2 REL
3
BHCS
2 REL
3
BPL
2 REL
3
BMI
2 REL
3
BMC
2 REL
3
BMS
2 REL
3
BIL
2 REL
3
BIH
2 REL
Read-Modify-Write
INH
IX1
5
6
1
NEGX
1 INH
4
CBEQX
3 IMM
7
DIV
1 INH
1
COMX
1 INH
1
LSRX
1 INH
4
LDHX
2 DIR
1
RORX
1 INH
1
ASRX
1 INH
1
LSLX
1 INH
1
ROLX
1 INH
1
DECX
1 INH
3
DBNZX
2 INH
1
INCX
1 INH
1
TSTX
1 INH
4
MOV
2 DIX+
1
CLRX
1 INH
4
NEG
2
IX1
5
CBEQ
3 IX1+
3
NSA
1 INH
4
COM
2 IX1
4
LSR
2 IX1
3
CPHX
3 IMM
4
ROR
2 IX1
4
ASR
2 IX1
4
LSL
2 IX1
4
ROL
2 IX1
4
DEC
2 IX1
5
DBNZ
3 IX1
4
INC
2 IX1
3
TST
2 IX1
4
MOV
3 IMD
3
CLR
2 IX1
SP1
IX
9E6
7
Control
INH
INH
8
9
Register/Memory
IX2
SP2
IMM
DIR
EXT
A
B
C
D
9ED
4
SUB
3 EXT
4
CMP
3 EXT
4
SBC
3 EXT
4
CPX
3 EXT
4
AND
3 EXT
4
BIT
3 EXT
4
LDA
3 EXT
4
STA
3 EXT
4
EOR
3 EXT
4
ADC
3 EXT
4
ORA
3 EXT
4
ADD
3 EXT
3
JMP
3 EXT
5
JSR
3 EXT
4
LDX
3 EXT
4
STX
3 EXT
4
SUB
3 IX2
4
CMP
3 IX2
4
SBC
3 IX2
4
CPX
3 IX2
4
AND
3 IX2
4
BIT
3 IX2
4
LDA
3 IX2
4
STA
3 IX2
4
EOR
3 IX2
4
ADC
3 IX2
4
ORA
3 IX2
4
ADD
3 IX2
4
JMP
3 IX2
6
JSR
3 IX2
4
LDX
3 IX2
4
STX
3 IX2
5
SUB
4 SP2
5
CMP
4 SP2
5
SBC
4 SP2
5
CPX
4 SP2
5
AND
4 SP2
5
BIT
4 SP2
5
LDA
4 SP2
5
STA
4 SP2
5
EOR
4 SP2
5
ADC
4 SP2
5
ORA
4 SP2
5
ADD
4 SP2
IX1
SP1
IX
E
9EE
F
LSB
0
Freescale Semiconductor
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
4
1
NEG
NEGA
2 DIR 1 INH
5
4
CBEQ CBEQA
3 DIR 3 IMM
5
MUL
1 INH
4
1
COM
COMA
2 DIR 1 INH
4
1
LSR
LSRA
2 DIR 1 INH
4
3
STHX
LDHX
2 DIR 3 IMM
4
1
ROR
RORA
2 DIR 1 INH
4
1
ASR
ASRA
2 DIR 1 INH
4
1
LSL
LSLA
2 DIR 1 INH
4
1
ROL
ROLA
2 DIR 1 INH
4
1
DEC
DECA
2 DIR 1 INH
5
3
DBNZ DBNZA
3 DIR 2 INH
4
1
INC
INCA
2 DIR 1 INH
3
1
TST
TSTA
2 DIR 1 INH
5
MOV
3 DD
3
1
CLR
CLRA
2 DIR 1 INH
INH Inherent
REL Relative
IMM Immediate
IX
Indexed, No Offset
DIR Direct
IX1 Indexed, 8-Bit Offset
EXT Extended
IX2 Indexed, 16-Bit Offset
DD Direct-Direct
IMD Immediate-Direct
IX+D Indexed-Direct DIX+ Direct-Indexed
*Pre-byte for stack pointer indexed instructions
5
3
NEG
NEG
3 SP1 1 IX
6
4
CBEQ
CBEQ
4 SP1 2 IX+
2
DAA
1 INH
5
3
COM
COM
3 SP1 1 IX
5
3
LSR
LSR
3 SP1 1 IX
4
CPHX
2 DIR
5
3
ROR
ROR
3 SP1 1 IX
5
3
ASR
ASR
3 SP1 1 IX
5
3
LSL
LSL
3 SP1 1 IX
5
3
ROL
ROL
3 SP1 1 IX
5
3
DEC
DEC
3 SP1 1 IX
6
4
DBNZ
DBNZ
4 SP1 2 IX
5
3
INC
INC
3 SP1 1 IX
4
2
TST
TST
3 SP1 1 IX
4
MOV
2 IX+D
4
2
CLR
CLR
3 SP1 1 IX
SP1 Stack Pointer, 8-Bit Offset
SP2 Stack Pointer, 16-Bit Offset
IX+ Indexed, No Offset with
Post Increment
IX1+ Indexed, 1-Byte Offset with
Post Increment
7
3
RTI
BGE
1 INH 2 REL
4
3
RTS
BLT
1 INH 2 REL
3
BGT
2 REL
9
3
SWI
BLE
1 INH 2 REL
2
2
TAP
TXS
1 INH 1 INH
1
2
TPA
TSX
1 INH 1 INH
2
PULA
1 INH
2
1
PSHA
TAX
1 INH 1 INH
2
1
PULX
CLC
1 INH 1 INH
2
1
PSHX
SEC
1 INH 1 INH
2
2
PULH
CLI
1 INH 1 INH
2
2
PSHH
SEI
1 INH 1 INH
1
1
CLRH
RSP
1 INH 1 INH
1
NOP
1 INH
1
STOP
*
1 INH
1
1
WAIT
TXA
1 INH 1 INH
2
SUB
2 IMM
2
CMP
2 IMM
2
SBC
2 IMM
2
CPX
2 IMM
2
AND
2 IMM
2
BIT
2 IMM
2
LDA
2 IMM
2
AIS
2 IMM
2
EOR
2 IMM
2
ADC
2 IMM
2
ORA
2 IMM
2
ADD
2 IMM
3
SUB
2 DIR
3
CMP
2 DIR
3
SBC
2 DIR
3
CPX
2 DIR
3
AND
2 DIR
3
BIT
2 DIR
3
LDA
2 DIR
3
STA
2 DIR
3
EOR
2 DIR
3
ADC
2 DIR
3
ORA
2 DIR
3
ADD
2 DIR
2
JMP
2 DIR
4
4
BSR
JSR
2 REL 2 DIR
2
3
LDX
LDX
2 IMM 2 DIR
2
3
AIX
STX
2 IMM 2 DIR
MSB
0
3
SUB
2 IX1
3
CMP
2 IX1
3
SBC
2 IX1
3
CPX
2 IX1
3
AND
2 IX1
3
BIT
2 IX1
3
LDA
2 IX1
3
STA
2 IX1
3
EOR
2 IX1
3
ADC
2 IX1
3
ORA
2 IX1
3
ADD
2 IX1
3
JMP
2 IX1
5
JSR
2 IX1
5
3
LDX
LDX
4 SP2 2 IX1
5
3
STX
STX
4 SP2 2 IX1
4
SUB
3 SP1
4
CMP
3 SP1
4
SBC
3 SP1
4
CPX
3 SP1
4
AND
3 SP1
4
BIT
3 SP1
4
LDA
3 SP1
4
STA
3 SP1
4
EOR
3 SP1
4
ADC
3 SP1
4
ORA
3 SP1
4
ADD
3 SP1
2
SUB
1 IX
2
CMP
1 IX
2
SBC
1 IX
2
CPX
1 IX
2
AND
1 IX
2
BIT
1 IX
2
LDA
1 IX
2
STA
1 IX
2
EOR
1 IX
2
ADC
1 IX
2
ORA
1 IX
2
ADD
1 IX
2
JMP
1 IX
4
JSR
1 IX
4
2
LDX
LDX
3 SP1 1 IX
4
2
STX
STX
3 SP1 1 IX
High Byte of Opcode in Hexadecimal
LSB
Low Byte of Opcode in Hexadecimal
0
5
Cycles
BRSET0 Opcode Mnemonic
3 DIR Number of Bytes / Addressing Mode
Central Processor Unit (CPU)
66
Table 6-2. Opcode Map
Bit Manipulation
DIR
DIR
Chapter 7
Internal Clock Generator Module (ICG)
7.1 Introduction
The internal clock generator module (ICG) is used to create a stable clock source for the microcontroller
without using any external components. The ICG generates the oscillator output clock (CGMXCLK),
which is used by the computer operating properly (COP), low-voltage inhibit (LVI), and other modules.
The ICG also generates the clock generator output (CGMOUT), which is fed to the system integration
module (SIM) to create the bus clocks. The bus frequency will be one-fourth the frequency of CGMXCLK
and one-half the frequency of CGMOUT. Finally, the ICG generates the timebase clock (TBMCLK), which
is used in the timebase module (TBM).
7.2 Features
Features of the ICG include:
• Selectable external clock generator, either one pin external source or two pin crystal, multiplexed
with port pins
• Internal clock generator with programmable frequency output in integer multiples of a nominal
frequency (307.2 kHz ± 25%)
• Frequency adjust (trim) register to improve variability to ± 2%
• Bus clock software selectable from either internal or external clock (bus frequency range from 76.8
kHz ± 25% to 9.75 MHz ± 25% in 76.8 kHz increments — note that for the MC68HC908KX8,
MC68HC908KX2, and MC68HC08KX8, do not exceed the maximum bus frequency of 8 MHz at
5.0 V and 4 MHz at 3.0 V
• Timebase clock automatically selected externally, if external clock is available
• Clock monitor for both internal and external clocks
7.3 Functional Description
As shown in Figure 7-1, the ICG contains these major submodules:
• Clock enable circuit
• Internal clock generator
• External clock generator
• Clock monitor circuit
• Clock selection circuit
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
67
Internal Clock Generator Module (ICG)
CS
CGMOUT
RESET
CGMXCLK
CLOCK
SELECTION
CIRCUIT
TBMCLK
IOFF
EOFF
CMON
ECGS
ICGS
CLOCK
MONITOR
CIRCUIT
FICGS
DDIV[3:0]
INTERNAL CLOCK
GENERATOR
N[6:0}
DSTG[7:0]
TRIM[7:0]
ICLK
IBASE
ICGEN
SIMOSCEN
CLOCK/PIN
ENABLE
CIRCUIT
OSCENINSTOP
EXTCLKEN
ECGON
ICGON
ECGEN
EXTXTALEN
EXTERNAL CLOCK
GENERATOR
EXTSLOW
PTB6
LOGIC
INTERNAL
TO MCU
ECLK
PTB7
LOGIC
OSC1
PTB6
OSC2
PTB7
EXTERNAL
NAME
CONFIGURATION (OR MOR) REGISTER BIT
NAME
REGISTER BIT
NAME
TOP LEVEL SIGNAL
NAME
MODULE SIGNAL
Figure 7-1. ICG Module Block Diagram
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
68
Freescale Semiconductor
Functional Description
7.3.1 Clock Enable Circuit
The clock enable circuit is used to enable the internal clock (ICLK) or external clock (ECLK) and the port
logic which is shared with the oscillator pins (OSC1 and OSC2). The clock enable circuit generates an
ICG stop (ICGSTOP) signal which stops all clocks (ICLK, ECLK, and the low-frequency base clock,
IBASE). ICGSTOP is set and the ICG is disabled in stop mode if the oscillator enable in stop
(OSCENINSTOP) bit in the CONFIG (or MOR) register is clear. The ICG clocks will be enabled in stop
mode if OSCENINSTOP is high.
The internal clock enable signal (ICGEN) turns on the ICG which generates ICLK. ICGEN is set (active)
whenever the ICGON bit is set and the ICGSTOP signal is clear. When ICGEN is clear, ICLK and IBASE
are both low.
The external clock enable signal (ECGEN) turns on the external clock generator which generates ECLK.
ECGEN is set (active) whenever the ECGON bit is set and the ICGSTOP signal is clear. ECGON cannot
be set unless the external clock enable (EXTCLKEN) bit in the CONFIG (or MOR) register is set. When
ECGEN is clear, ECLK is low.
The port B6 enable signal (PB6EN) turns on the port B6 logic. Since port B6 is on the same pin as OSC1,
this signal is only active (set) when the external clock function is not desired. Therefore, PB6EN is clear
when ECGON is set. PB6EN is not gated with ICGSTOP, which means that if the ECGON bit is set, the
port B6 logic will remain disabled in stop mode.
The port B7 enable signal (PB7EN) turns on the port B7 logic. Since port B7 is on the same pin as OSC2,
this signal is only active (set) when two-pin oscillator function is not desired. Therefore, PB7EN is clear
when ECGON and the external crystal enable (EXTXTALEN) bit in the CONFIG (or MOR) register are
both set. PB6EN is not gated with ICGSTOP, which means that if ECGON and EXTXTALEN are set, the
port B7 logic will remain disabled in stop mode.
7.3.2 Internal Clock Generator
The ICG, shown in Figure 7-2, creates a low frequency base clock (IBASE), which operates at a nominal
frequency (fNOM) of 307.2 kHz ± 25%, and an internal clock (ICLK) which is an integer multiple of IBASE.
This multiple is the ICG multiplier factor (N), which is programmed in the ICG multiplier register (ICGMR).
The ICG is turned off and the output clocks (IBASE and ICLK) are held low when the ICG enable signal
(ICGEN) is clear.
The ICG contains:
• A digitally controlled oscillator
• A modulo "N" divider
• A frequency comparator, which contains voltage and current references, a frequency to voltage
converter, and comparators
• A digital loop filter
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
69
Internal Clock Generator Module (ICG)
ICGEN
VOLTAGE AND
CURRENT
REFERENCES
FICGS
++
DSTG[7:0]
DDIV[3:0]
DIGITAL
LOOP FILTER
DIGITALLY
CONTROLLED
OSCILLATOR
ICLK
--
TRIM[7:0]
FREQUENCY
COMPARATOR
CLOCK GEN
N[6:0]
MODULO
"N"
DIVIDER
IBASE
NAME
CONFIG (OR MOR) REGISTER BIT
NAME
REGISTER BIT
NAME
TOP LEVEL SIGNAL
NAME
MODULE SIGNAL
Figure 7-2. Internal Clock Generator Block Diagram
7.3.2.1 Digitally Controlled Oscillator
The digitally controlled oscillator (DCO) is an inaccurate oscillator which generates the internal clock
(ICLK). The clock period of ICLK is dependent on the digital loop filter outputs (DSTG[7:0] and DDIV[3:0]).
Because there is only a limited number of bits in DDIV and DSTG, the precision of the output (ICLK) is
restricted to a precision of approximately ±0.202% to ±0.368% when measured over several cycles (of
the desired frequency). Additionally, since the propagation delays of the devices used in the DCO ring
oscillator are a measurable fraction of the bus clock period, reaching the long-term precision may require
alternately running faster and slower than desired, making the worst case cycle-to-cycle frequency
variation ±6.45% to ±11.8% (of the desired frequency). The valid values of DDIV:DSTG range from $000
to $9FF. For more information on the quantization error in the DCO, see 7.4.4 Quantization Error in DCO
Output.
7.3.2.2 Modulo "N" Divider
The modulo "N" divider creates the low frequency base clock (IBASE) by dividing the internal clock (ICLK)
by the ICG multiplier factor (N), contained in the ICG multiplier register (ICGMR). When N is programmed
to a $01 or $00, the divider is disabled and ICLK is passed through to IBASE undivided. When the ICG is
stable, the frequency of IBASE will be equal to the nominal frequency (fNOM) of 307.2 kHz ± 25%.
7.3.2.3 Frequency Comparator
The frequency comparator effectively compares the low frequency base clock (IBASE) to a nominal
frequency, fNOM. First, the frequency comparator converts IBASE to a voltage by charging a known
capacitor with a current reference for a period dependent on IBASE. This voltage is compared to a voltage
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
70
Freescale Semiconductor
Functional Description
reference with comparators, whose outputs are fed to the digital loop filter. The dependence of these
outputs on the capacitor size, current reference, and voltage reference causes up to ±25% error in fNOM.
7.3.2.4 Digital Loop Filter
The digital loop filter (DLF) uses the outputs of the frequency comparator to adjust the internal clock
(ICLK) clock period. The DLF generates the DCO divider control bits (DDIV[3:0]) and the DCO stage
control bits (DSTG[7:0]), which are fed to the DCO. The DLF first concatenates the DDIV and DSTG
registers (DDIV[3:0]:DSTG[7:0]) and then adds or subtracts a value dependent on the relative error in the
low frequency base clock’s period, as shown in Table 7-1. In some extreme error conditions, such as
operating at a VDD level which is out of specification, the DLF may attempt to use a value above the
maximum ($9FF) or below the minimum ($000). In both cases, the value for DDIV will be between $A and
$F. In this range, the DDIV value will be interpreted the same as $9 (the slowest condition). Recovering
from this condition requires subtracting (increasing frequency) in the normal fashion until the value is
again below $9FF (if the desired value is $9xx, the value may settle at $Axx through $Fxx — this is an
acceptable operating condition). If the error is less than ±15%, the ICG’s filter stable indicator (FICGS) is
set, indicating relative frequency accuracy to the clock monitor.
All FLASH mask sets other than 0K45D, 1K45D, 0L09H, 1L09H have 15% comparators that improve
stability at low temperatures.
Table 7-1. Correction Sizes from DLF to DCO
Frequency Error
of IBASE compared
to fNOM
DDVI[3:0]:DSTG[7:0]
Correction
IBASE < 0.85 fNOM
–32 (–$020)
0.85 fNOM < IBASE
IBASE < fNOM
–1 (–$001)
fNOM < IBASE
IBASE < 1.15 fNOM
+1 (+$001)
1.15 fNOM < IBASE
+32 (+$020)
Current to New
DDIV[3:0]:DSTG[7:0] (1)
Relative Correction
in DCO
Minimum
$xFF to $xDF
–2/31
–6.45%
Maximum
$x20 to $x00
–2/19
–10.5%
Minimum
$xFF to $xFE
–0.0625/31
–0.202%
Maximum
$x01 to $x00
–0.0625/17.0625
–0.366%
Minimum
$xFE to $xFF
+0.0625/30.9375
+0.202%
Maximum
$x00 to $x01
+0.0625/17
+0.368%
Minimum
$xDF to $xFF
+2/29
+6.90%
Maximum
$x00 to $x20
+2/17
+11.8%
1. x =Maximum error is independent of value in DDIV[3:0]. DDIV increments or decrements when an addition to DSTG[7:0]
carries or borrows.
7.3.3 External Clock Generator
The ICG also provides for an external oscillator or external clock source, if desired. The external clock
generator, shown in Figure 7-3, contains an external oscillator amplifier and an external clock input path.
7.3.3.1 External Oscillator Amplifier
The external oscillator amplifier provides the gain required by an external crystal connected in a Pierce
oscillator configuration. The amount of this gain is controlled by the slow external (EXTSLOW) bit in the
CONFIG (or MOR) register. When EXTSLOW is set, the amplifier gain is reduced for operating
low-frequency crystals (32 kHz to 100 kHz). When EXTSLOW is clear, the amplifier gain will be sufficient
for 1 MHz to 8 MHz crystals. EXTSLOW must be configured correctly for the given crystal or the circuit
may not operate.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
71
Internal Clock Generator Module (ICG)
ECGEN
ECLK
INPUT PATH
EXTXTALEN
AMPLIFIER
EXTERNAL
CLOCK
GENERATOR
EXTSLOW
INTERNAL TO MCU
OSC1
PTB6
OSC2
PTB7
EXTERNAL
NAME
NAME
RB
R S*
CONFIGURATION (OR MOR) BIT
X1
TOP LEVEL SIGNAL
NAME
REGISTER BIT
NAME
MODULE SIGNAL
C1
*RS can be 0 (shorted)
when used with higherfrequency crystals. Refer
to manufacturer’s data.
C2
These components are required
for external crystal use only.
Figure 7-3. External Clock Generator Block Diagram
The amplifier is enabled when the external clock generator enable (ECGEN) signal is set and when the
external crystal enable (EXTXTALEN) bit in the CONFIG (or MOR) register is set. ECGEN is controlled
by the clock enable circuit (see 7.3.1 Clock Enable Circuit), and indicates that the external clock function
is desired. When enabled, the amplifier will be connected between the PTB6/(OSC1) and
PTB7/(OSC2)/RST pins. Otherwise, the PTB7/(OSC2)/RST pin reverts to its port function. In its typical
configuration, the external oscillator requires five external components:
• Crystal, X1
• Fixed capacitor, C1
• Tuning capacitor, C2 (can also be a fixed capacitor)
• Feedback resistor, RB
• Series resistor, RS (included in the diagram to follow strict Pierce oscillator guidelines and may not
be required for all ranges of operation, especially with high frequency crystals. Refer to the crystal
manufacturer’s data for more information.)
7.3.3.2 External Clock Input Path
The external clock input path is the means by which the microcontroller uses an external clock source.
The input to the path is the PTB6/(OSC1) pin and the output is the external clock (ECLK). The path, which
contains input buffering, is enabled when the external clock generator enable signal (ECGEN) is set.
When not enabled, the PTB6/(OSC1) pin reverts to its port function.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
72
Freescale Semiconductor
Functional Description
7.3.4 Clock Monitor Circuit
The ICG contains a clock monitor circuit which, when enabled, will continuously monitor both the external
clock (ECLK) and the internal clock (ICLK) to determine if either clock source has been corrupted. The
clock monitor circuit, shown in Figure 7-4, contains these blocks:
• Clock monitor reference generator
• Internal clock activity detector
• External clock activity detector
IOFF
IOFF
EREF
ICGS
ICGS
IBASE
EREF
CMON
CMON
FICGS
FICGS
IBASE
IBASE
ICGEN
ICGEN
ICLK
ACTIVITY
DETECTOR
ICGON
EXTXTALEN
EXTSLOW
EXTXTALEN
EXTSLOW
REFERENCE
GENERATOR
ECGS
ESTBCLK
ECLK
ECGEN
IREF
ESTBCLK
ECGS
ECGS
IREF
ECGEN
ECLK
ECGEN
ECLK
ECLK
ACTIVITY
DETECTOR
CMON
EOFF
EOFF
NAME
CONFIGURATION (OR MOR) REGISTER BIT
NAME
REGISTER BIT
NAME
TOP LEVEL SIGNAL
NAME
MODULE SIGNAL
Figure 7-4. Clock Monitor Block Diagram
7.3.4.1 Clock Monitor Reference Generator
The clock monitor uses a reference based on one clock source to monitor the other clock source. The
clock monitor reference generator generates the external reference clock (EREF) based on the external
clock (ECLK) and the internal reference clock (IREF) based on the internal clock (ICLK). To simplify the
circuit, the low frequency base clock (IBASE) is used in place of ICLK because it always operates at or
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
73
Internal Clock Generator Module (ICG)
near 307.2 kHz. For proper operation, EREF must be at least twice as slow as IBASE and IREF must be
at least twice as slow as ECLK.
To guarantee that IREF is slower than ECLK and EREF is slower than IBASE, one of the signals is divided
down. Which signal is divided and by how much is determined by the external slow (EXTSLOW) and
external crystal enable (EXTXTALEN) bits in the CONFIG (or MOR) register, according to the rules in
Table 7-2.
NOTE
Each signal (IBASE and ECLK) is always divided by four. A longer divider
is used on either IBASE or ECLK based on the EXTSLOW bit.
ICGON
ECGON
ECGS
EXTSLOW
EXTXTALEN
Table 7-2. Clock Monitor Reference Divider Ratios
External
Frequency
0
x
x
x
x
U
U
U
U
U
Off
0
x
0
0
x
x
0
Off
0
Off
0
U
U
1
1
0
x
0
Off
0
16
(ECLK)
2.0 MHz
1*4
76.8 kHz
± 25%
1
1
0
x
1
Off
0
4096
(ECLK)
7.324 kHz
1*4
76.8 kHz
± 25%
1
1
1
0
0
16
(ECLK)
19.2 kHz
1*4
76.8 kHz
± 25%
1
1
1
0
1
4096
(ECLK)
244 Hz
1.953 kHz
1*4
76.8 kHz
± 25%
1
1
1
1
0
16
(IBASE)(2)
19.2 kHz
± 25%
4096*4
18.75 Hz
± 125%
1
1
1
1
1
4096
(IBASE)(2)
75 Hz
± 25%
16*4
4.8 kHz
± 25%
Minimum
60 Hz
Maximum
32 MHz
Minimum
30 kHz
Maximum
8 MHz
Minimum
307.2 kHz
Maximum
32 MHz
Minimum
1 MHz
Maximum
8 MHz
Minimum
60 Hz
Maximum
307.2 kHz
Minimum
30 kHz
Maximum
100 kHz
EREF
Divider
Ratio
EREF
Frequency
ESTBCLK
Divider
Ratio
ESTBCLK
Frequency
IREF
Divider
Ratio(1)
IREF
Frequency
128*4
128*4
1*4
1*4
600 Hz
62.5 kHz
1.953 kHz
15.63 kHz
15 Hz
76.8 kHz
7.5 kHz
25.0 kHz
3.75 Hz
1.953 kHz
2.0 MHz
1. U = Unaffected; refer to section of table where ICGON or ECGON is set to 1.
2. IBASE is always used as the internal frequency (307.2 kHz).
To conserve size, the long divider (divide by 4096) is also used as an external crystal stabilization divider.
The divider is reset when the external clock generator is turned off or in STOP (ECGEN is clear). When
the external clock generator is first turned on, the external clock generator stable bit (ECGS) will be clear.
This condition automatically selects ECLK as the input to the long divider. The external stabilization clock
(ESTBCLK) will be ECLK divided by 16 when EXTXTALEN is low or 4096 when EXTXTALEN is high.
This time-out allows the crystal to stabilize. The falling edge of ESTBCLK is used to set ECGS (ECGS will
set after a full 16 or 4096 cycles). When ECGS is set, the divider returns to its normal function. ESTBCLK
may be generated by either IBASE or ECLK, but any clocking will only reinforce the set condition. If ECGS
is cleared because the clock monitor determined that ECLK was inactive, the divider will revert to a
stabilization divider. Since this will change the EREF and IREF divide ratios, it is important to turn the
clock monitor off (CMON = 0) after inactivity is detected to ensure valid recovery.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
74
Freescale Semiconductor
Functional Description
7.3.4.2 Internal Clock Activity Detector
The internal clock activity detector, shown in Figure 7-5, looks for at least one falling edge on the
low-frequency base clock (IBASE) every time the external reference (EREF) is low. Since EREF is less
than half the frequency of IBASE, this should occur every time. If it does not occur two consecutive times,
the internal clock inactivity indicator (IOFF) is set. IOFF will be cleared the next time there is a falling edge
of IBASE while EREF is low.
The internal clock stable bit (ICGS) is also generated in the internal clock activity detector. ICGS is set
when the internal clock generator’s filter stable signal (FICGS) indicates that IBASE is within about 15%
of the target 307.2 kHz ± 25% for two consecutive measurements. ICGS is cleared when FICGS is clear,
the internal clock generator is turned off or in STOP (ICGEN is clear), or when IOFF is set.
CMON
CK
EREF
IOFF
Q
1/4
R
R
R
D
D
DFFRS
IBASE
CK
Q
S
R
Q
DFFRR
CK
D
Q
ICGS
DFFRR
CK
R
R
DLF MEASURE
OUTPUT CLOCK
ICGEN
FICGS
NAME
CONFIGURATION (OR MOR) REGISTER BIT
NAME
REGISTER BIT
NAME
TOP LEVEL SIGNAL
NAME
MODULE SIGNAL
Figure 7-5. Internal Clock Activity Detector
7.3.4.3 External Clock Activity Detector
The external clock activity detector, shown in Figure 7-6, looks for at least one falling edge on the external
clock (ECLK) every time the internal reference (IREF) is low. Since IREF is less than half the frequency
of ECLK, this should occur every time. If it does not occur two consecutive times, the external clock
inactivity indicator (EOFF) is set. EOFF will be cleared the next time there is a falling edge of ECLK while
IREF is low.
The external clock stable bit (ECGS) is also generated in the external clock activity detector. ECGS is set
on a falling edge of the external stabilization clock (ESTBCLK). This will be 4096 ECLK cycles after the
external clock generator on bit is set or the MCU exits STOP (ECGEN = 1) if the external crystal enable
(EXTXTALEN) in the CONFIG (or MOR) register is set, or 16 cycles when EXTXTALEN is clear. ECGS
is cleared when the external clock generator is turned off or in STOP (ECGEN is clear) or when EOFF is
set.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
75
Internal Clock Generator Module (ICG)
CMON
CK
IREF
EOFF
Q
1/4
R
R
R
D
D
DFFRS
CK
ECLK
DFFRR
CK
Q
S
Q
EGGS
R
ESTBCLK
ECGEN
NAME
CONFIGURATION (OR MOR) REGISTER BIT
NAME
REGISTER BIT
NAME
TOP LEVEL SIGNAL
NAME
MODULE SIGNAL
Figure 7-6. External Clock Activity Detector
7.3.5 Clock Selection Circuit
The clock selection circuit, shown in Figure 7-7, contains two clock switches which generate the oscillator
output clock (CGMXCLK) and the timebase clock (TBMCLK) from either the internal clock (ICLK) or the
external clock (ECLK). The clock selection circuit also contains a divide-by-two circuit which creates the
clock generator output clock (CGMOUT), which generates the bus clocks.
CS
SELECT
ICLK
ICLK
ECLK
ECLK
IOFF
IOFF
EOFF
EOFF
RESET
VSS
ECGON
CGMXCLK
OUTPUT
SYNCHRONIZING
CLOCK
SWITCHER
DIV2
CGMOUT
FORCE_I
FORCE_E
SELECT
TBMCLK
OUTPUT
ICLK
ECLK
IOFF
EOFF
SYNCHRONIZING
CLOCK
SWITCHER
FORCE_I
FORCE_E
NAME
CONFIGURATION (OR MOR) REGISTER BIT
NAME
REGISTER BIT
NAME
TOP LEVEL SIGNAL
NAME
MODULE SIGNAL
Figure 7-7. Clock Selection Circuit Block Diagram
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
76
Freescale Semiconductor
Usage Notes
7.3.5.1 Clock Selection Switches
The first switch creates the oscillator output clock (CGMXCLK) from either the internal clock (ICLK) or the
external clock (ECLK), based on the clock select bit (CS set selects ECLK, clear selects ICLK). When
switching the CS bit, both ICLK and ECLK must be on (ICGON and ECGON set). The clock being
switched to must also be stable (ICGS or ECGS set).
The second switch creates the timebase clock (TBMCLK) from ICLK or ECLK based on the external clock
on bit. When ECGON is set, the switch automatically selects the external clock, regardless of the state of
the ECGS bit.
7.3.5.2 Clock Switching Circuit
To robustly switch between the internal clock (ICLK) and the external clock (ECLK), the switch assumes
the clocks are completely asynchronous, so a synchronizing circuit is required to make the transition.
When the select input (the clock select bit for the oscillator output clock switch or the external clock on bit
for the timebase clock switch) is changed, the switch will continue to operate off the original clock for
between 1 and 2 cycles as the select input is transitioned through one side of the synchronizer. Next, the
output will be held low for between 1 and 2 cycles of the new clock as the select input transitions through
the other side. Then the output starts switching at the new clock’s frequency. This transition guarantees
that no glitches will be seen on the output even though the select input may change asynchronously to
the clocks. The unpredictability of the transition period is a necessary result of the asynchronicity.
The switch automatically selects ICLK during reset. When the clock monitor is on (CMON is set) and it
determines one of the clock sources is inactive (as indicated by the IOFF or EOFF signals), the circuit is
forced to select the active clock. There are no clocks for the inactive side of the synchronizer to properly
operate, so that side is forced deselected. However, the active side will not be selected until 1 to 2 clock
cycles after the IOFF or EOFF signal transitions.
7.4 Usage Notes
The ICG has several features which can provide protection to the microcontroller if properly used. There
are other features which can greatly simplify usage if certain techniques are employed. This subsection
will describe several possible ways to use the ICG and its features. These techniques are not the only
ways to use the ICG, and may not be optimum for all environments. In any case, these techniques should
only be used as a template, and the user should modify them according to the application’s requirements.
These notes include:
• Switching clock sources
• Enabling the clock monitor
• Using clock monitor interrupts
• Quantization error in DCO output
• Switching internal clock frequencies
• Nominal frequency settling time
• Improving frequency settling time
• Trimming frequency
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
77
Internal Clock Generator Module (ICG)
7.4.1 Switching Clock Sources
Switching from one clock source to another requires both clock sources to be enabled and stable. A
simple flow requires:
1. Enable desired clock source
2. Wait for it to become stable
3. Switch clocks
4. Disable previous clock source
The key point to remember in this flow is that the clock source cannot be switched (CS cannot be written)
unless the desired clock is on and stable. A short assembly code example of how to employ this flow is
shown in Figure 7-8. This code is for illustrative purposes only and does not represent valid syntax for any
particular assembler.
start
lda
#$13
loop
**
**
sta
icgcr
cmpa
bne
icgcr
loop
;Clock Switching Code Example
;This code switches from Internal to External clock
;Clock Monitor and interrupts are not enabled
;Mask for CS, ECGON, ECGS
; If switching from External to Internal, mask is $0C.
;Other code here, such as writing the COP, since ECGS may
; take some time to set
;Try to set CS, ECGON and clear ICGON. ICGON will not
; clear until CS is set, and CS will not set until
; ECGON and ECGS are set.
;Check to see if ECGS set, then CS set, then ICGON clear
;Keep looping until ICGON is clear.
Figure 7-8. Code Example for Switching Clock Sources
7.4.2 Enabling the Clock Monitor
Many applications require the clock monitor to determine if one of the clock sources has become inactive,
so the other can be used to recover from a potentially dangerous situation. Using the clock monitor
requires both clocks to be active (ECGON and ICGON both set). To enable the clock monitor, both clocks
must also be stable (ECGS and ICGS both set). This is to prevent the use of the clock monitor when a
clock is first turned on and potentially unstable.
Enabling the clock monitor and clock monitor interrupts requires a flow similar to the one below:
1. Enable the alternate clock source
2. Wait for both clock sources to be stable
3. Switch to the desired clock source if necessary
4. Enable the clock monitor
5. Enable clock monitor interrupts
These events must happen in sequence. A short assembly code example of how to employ this flow is
shown in Figure 7-9. This code is for illustrative purposes only and does not represent valid syntax for any
particular assembler.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
78
Freescale Semiconductor
Usage Notes
start
lda
loop
**
sta
brset
cmpa
bne
;Clock Monitor Enabling Code Example
;This code turns on both clocks, selects the desired
; one, then turns on the Clock Monitor and Interrupts
#$AF
;Mask for CMIE, CMON, ICGON, ICGS, ECGON, ECGS
; If Internal Clock desired, mask is $AF
; If External Clock desired, mask is $BF
; If interrupts not desired mask is $2F int; $3F ext
**
;Other code here, such as writing the COP, since ECGS
; and ICGS may take some time to set.
icgcr
;Try to set CMIE. CMIE wont set until CMON set; CMON
; won’t set until ICGON, ICGS, ECGON, ECGS set.
6,ICGCR,error ;Verify CMF is not set
icgcr
;Check if ECGS set, then CMON set, then CMIE set
loop
;Keep looping until CMIE is set.
Figure 7-9. Code Example for Enabling the Clock Monitor
7.4.3 Using Clock Monitor Interrupts
The clock monitor circuit can be used to recover from perilous situations such as crystal loss. To use the
clock monitor effectively, the following notes should be observed:
• Enable the clock monitor and clock monitor interrupts.
• The first statement in the clock monitor interrupt service routine (CMISR) should be a read to the
ICG control register (ICGCR) to verify the clock monitor flag (CMF) is set. This is also the first step
in clearing the CMF bit.
• The second statement in the CMISR should be a write to the ICGCR to clear the CMF bit (write the
bit low). Writing the bit high will not affect it. This statement does not need to immediately follow
the first, but must be contained in the CMISR.
• The third statement in the CMISR should be to clear the CMON bit. This is required to ensure
proper reconfiguration of the reference dividers. This statement must also be contained in the
CMISR.
• Although the clock monitor can only be enabled when both clocks are stable (ICGS is set or ECGS
is set), it will remain set if one of the clocks goes unstable.
• The clock monitor only works if the external slow (EXTSLOW) bit in the CONFIG (or MOR) register
is set to the correct value.
• The internal and external clocks must both be enabled and running in order to use the clock
monitor.
• When the clock monitor detects inactivity, the inactive clock is automatically deselected and the
active clock selected as the source for CGMXCLK and TBMCLK. The CMISR can use the state of
the CS bit to check which clock is inactive.
• When the clock monitor detects inactivity, the application may have been subjected to extreme
conditions which may have affected other circuits. The CMISR should take any appropriate
precautions.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
79
Internal Clock Generator Module (ICG)
7.4.4 Quantization Error in DCO Output
The digitally controlled oscillator (DCO) is comprised of three major sub-blocks:
• Binary weighted divider
• Variable-delay ring oscillator
• Ring oscillator fine-adjust circuit
Each of these blocks affects the clock period of the internal clock (ICLK). Since these blocks are controlled
by the digital loop filter (DLF) outputs DDIV and DSTG, the output of the DCO can only change in
quantized steps as the DLF increments or decrements its output. The following subsections describe how
each block will affect the output frequency.
7.4.4.1 Digitally Controlled Oscillator
The digitally controlled oscillator (DCO) is an inaccurate oscillator which generates the internal clock
(ICLK), whose clock period is dependent on the digital loop filter outputs (DSTG[7:0] and DDIV[3:0]).
Because of the digital nature of the DCO, the clock period of ICLK will change in quantized steps. This
will create a clock period difference, or quantization error (Q-ERR) from one cycle to the next. Over
several cycles or for longer periods, this error is divided out until it reaches a minimum error of 0.202% to
0.368%. The dependence of this error on the DDIV[3:0] value and the number of cycles the error is
measured over is shown in Table 7-3.
Table 7-3. Quantization Error in ICLK
DDIV[3:0]
τICLK Q-ERR
ICLK Cycles
Bus Cycles
%0000 (min)
1
NA
6.45% – 11.8%
%0000 (min)
4
1
1.61% – 2.94%
%0000 (min)
≥ 32
≥8
0.202% – 0.368%
%0001
1
NA
3.23% – 5.88%
%0001
4
1
0.806% – 1.47%
%0001
≥ 16
≥4
0.202% – 0.368%
%0010
1
NA
1.61% – 2.94%
%0010
4
1
0.403% – 0.735%
%0010
≥8
≥2
0.202% – 0.368%
%0011
1
NA
0.806% – 1.47%
%0011
≥4
≥1
0.202% – 0.368%
%0100
1
NA
0.403% – 0.735%
%0100
≥2
≥1
0.202% – 0.368%
%0101 – %1001 (max)
≥1
≥1
0.202% – 0.368%
7.4.4.2 Binary Weighted Divider
The binary weighted divider divides the output of the ring oscillator by a power of 2, specified by the DCO
divider control bits (DDIV[3:0]). DDIV maximizes at %1001 (values of %1010 through %1111 are
interpreted as %1001), which corresponds to a divide by 512. When DDIV is %0000, the ring oscillator’s
output is divided by 1. Incrementing DDIV by one will double the period; decrementing DDIV will halve the
period. The DLF cannot directly increment or decrement DDIV; DDIV is only incremented or decremented
when an addition or subtraction to DSTG carries or borrows.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
80
Freescale Semiconductor
Usage Notes
7.4.4.3 Variable-Delay Ring Oscillator
The variable-delay ring oscillator’s period is adjustable from 17 to 31 stage delays, in increments of two,
based on the upper three DCO stage control bits (DSTG[7:5]). A DSTG[7:5] of %000 corresponds to 17
stage delays; DSTG[7:5] of %111 corresponds to 31 stage delays. Adjusting the DSTG[5] bit has a 6.45%
to 11.8% effect on the output frequency. This also corresponds to the size correction made when the
frequency error is greater than ±15%. The value of the binary weighted divider does not affect the relative
change in output clock period for a given change in DSTG[7:5].
7.4.4.4 Ring Oscillator Fine-Adjust Circuit
The ring oscillator fine-adjust circuit causes the ring oscillator to effectively operate at non-integer
numbers of stage delays by operating at two different points for a variable number of cycles specified by
the lower five DCO stage control bits (DSTG[4:0]). For example, when DSTG[7:5] is %011, the ring
oscillator nominally operates at 23 stage delays. When DSTG[4:0] is %00000, the ring will always operate
at 23 stage delays. When DSTG[4:0] is %00001, the ring will operate at 25 stage delays for one of 32
cycles and at 23 stage delays for 31 of 32 cycles. Likewise, when DSTG[4:0] is %11111, the ring operates
at 25 stage delays for 31 of 32 cycles and at 23 stage delays for one of 32 cycles. When DSTG[7:5] is
%111, similar results are achieved by including a variable divide-by-two, so the ring operates at 31 stages
for some cycles and at 17 stage delays, with a divide-by-two for an effective 34 stage delays, for the
remainder of the cycles. Adjusting the DSTG[0] bit has a 0.202% to 0.368% effect on the output clock
period. This corresponds to the minimum size correction made by the DLF, and the inherent, long term
quantization error in the output frequency.
7.4.5 Switching Internal Clock Frequencies
The frequency of the internal clock (ICLK) may need to be changed for some applications. For example,
if the reset condition does not provide the correct frequency, or if the clock is slowed down for a low power
mode (or sped up after a low-power mode), the frequency must be changed by programming the internal
clock multiplier factor (N). The frequency of ICLK is N times the frequency of IBASE, which is 307.2 kHz
± 25%.
Before switching frequencies by changing the N value, the clock monitor must be disabled. This is
because when N is changed, the frequency of the low-frequency base clock (IBASE) will change
proportionally until the digital loop filter has corrected the error. Since the clock monitor uses IBASE, it
could erroneously detect an inactive clock. The clock monitor cannot be re-enabled until the Internal Clock
is stable again (ICGS is set).
The following flow is an example of how to change the clock frequency:
• Verify there is no clock monitor Interrupt by reading the CMF bit
• Turn off the clock monitor
• If desired, switch to the external clock (see 7.4.1 Switching Clock Sources)
• Change the value of N
• Switch back to internal (see 7.4.1 Switching Clock Sources), if desired
• Turn on the clock monitor (see 7.4.2 Enabling the Clock Monitor), if desired
7.4.6 Nominal Frequency Settling Time
Because the clock period of the internal clock (ICLK) is dependent on the digital loop filter outputs (DDIV
and DSTG) which cannot change instantaneously, ICLK will temporarily operate at an incorrect clock
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
81
Internal Clock Generator Module (ICG)
period when any of the operating condition changes. This happens whenever the part is reset, the ICG
multiply factor (N) is changed, the ICG trim factor (TRIM) is changed, or the internal clock is enabled after
inactivity (STOP or disabled operation). The time that the ICLK takes to adjust to the correct period is
known as the settling time.
Settling time depends primarily on how many corrections it takes to change the clock period, and the
period of each correction. Since the corrections require four periods of the low-frequency base clock
(4*τIBASE), and since ICLK is N (the ICG multiply factor for the desired frequency) times faster than
IBASE, each correction takes 4*N*τICLK. The period of ICLK, however, will vary as the corrections occur.
7.4.6.1 Settling To Within 15%
All FLASH mask sets other than 0K45D, 1K45D, 0L09H, 1L09H have 15% comparators that improve
stability at low temperatures.
When the error is greater than 15%, the filter takes eight corrections to double or halve the clock period.
Due to how the DCO increases or decreases the clock period, the total period of these eight corrections
is approximately 11 times the period of the fastest correction. (If the corrections were perfectly linear, the
total period would be 11.5 times the minimum period; however, the ring must be slightly nonlinear.)
Therefore, the total time it takes to double or halve the clock period is 44*N*tICLKFAST.
If the clock period needs more than doubled or halved, the same relationship applies, only for each time
the clock period needs doubled, the total number of cycles doubles. That is, when transitioning from fast
to slow, going from the initial speed to half speed takes 44*N*tICLKFAST; from half speed to quarter speed
takes 88*N*tICLKFAST; going from quarter speed to eighth speed takes 176*N*tICLKFAST; and so on. This
series can be expressed as (2x-1)*44*N*tICLKFAST, where x is the number of times the speed needs
doubled or halved. Since 2x happens to be equal to τICLKSLOW/τICLKFAST, the equation reduces to
44*N*(τICLKSLOW-τICLKFAST).
NOTE
Increasing speed takes much longer than decreasing speed since N is
higher. This can be expressed in terms of the initial clock period (τ1) minus
the final clock period (τ2) as such:
τ
15
= abs [ 44N ( τ – τ ) ]
1 2
Once the clock period is within 15% of the desired clock period, the internal clock stable bit (ICGS) will be
set and the clock frequency is usable, although the error will be as high as 15%.
7.4.6.2 Total Settling Time
Once the clock period is within 15% of the desired clock period, the filter starts making minimum
adjustments. In this mode, each correction will adjust the frequency between 0.202% and 0.368%. A
maximum of 88 corrections will be required to get to the minimum error. Each correction takes
approximately the same period of time, or 4*τIBASE. This makes 88 corrections (352*τIBASE) to get from
15% to the minimum error. The total time to the minimum error is:
τ
tot
= abs [ 44N ( τ – τ ) ] + 352τ
1 2
IBASE
The equations for τ15, τ5, and τtot are dependent on the actual initial and final clock periods τ1 and τ2, not
the nominal. This means the variability in the ICLK frequency due to process, temperature and voltage
must be considered. Additionally, other process factors and noise can affect the actual tolerances of the
points at which the filter changes modes. This means a worst case adjustment of up to 35% (ICLK clock
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
82
Freescale Semiconductor
Low-Power Modes
period tolerance plus 10%) must be added. This adjustment can be reduced with trimming. Table 7-4
shows some typical values for settling time.
Table 7-4. Typical Settling Time Examples
τ1
τ2
1/ (6.45 MHz)
1/ (25.8 MHz)
1/ (25.8 MHz)
1/ (6.45 MHz)
1/ (25.8 MHz)
1/ (307.2 kHz)
1/ (307.2 kHz)
1/ (25.8 MHz)
τ15
τtot
84
430 µs
1165 µs
21
107 µs
840 µs
1
141 µs
875 µs
84
11.9 ms
12.6 ms
N
7.4.7 Trimming Frequency on the Internal Clock Generator
The unadjusted frequency of the low-frequency base clock (IBASE), when the comparators in the
frequency comparator indicate zero error, will vary as much as ±25% due to process, temperature, and
voltage dependencies. These dependencies are in the voltage and current references, the offset of the
comparators, and the internal capacitor. The voltage and temperature dependencies have been designed
to be a maximum of approximately ±1% error. The process dependencies account for the rest.
Fortunately, for an individual part, the process dependencies are constant. An individual part can operate
at approximately ±2% variance from its unadjusted operating point over the entire spec range of the
application. If the unadjusted operating point can be changed, the entire variance can be limited to ±2%.
The method of changing the unadjusted operating point is by changing the size of the capacitor. This
capacitor is designed with 639 equally sized units. 384 of these units are always connected. The
remaining 255 units are put in by adjusting the ICG trim factor (TRIM). The default value for TRIM is $80,
or 128 units, making the default capacitor size 512. Each unit added or removed will adjust the output
frequency by about ±0.195% of the unadjusted frequency (adding to TRIM will decrease frequency).
Therefore, the frequency of IBASE can be changed to ±25% of its unadjusted value, which is enough to
cancel the process variability mentioned before.
The best way to trim the internal clock is to use the timer to measure the width of an input pulse on an
input capture pin (this pulse must be supplied by the application and should be as long or wide as
possible). Considering the prescale value of the timer and the theoretical (zero error) frequency of the bus
(307.2 kHz *N/4), the error can be calculated. This error, expressed as a percentage, can be divided by
0.195% and the resultant factor added or subtracted from TRIM. This process should be repeated to
eliminate any residual error.
7.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
7.5.1 Wait Mode
The ICG remains active in wait mode. If enabled, the ICG interrupt to the CPU can bring the MCU out of
wait mode.
In some applications, low power consumption is desired in wait mode and a high frequency clock is not
needed. In these applications, reduce power consumption by either selecting a low-frequency external
clock and turn the internal clock generator off, or reduce the bus frequency by minimizing the ICG
multiplier factor (N) before executing the WAIT instruction.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
83
Internal Clock Generator Module (ICG)
7.5.2 Stop Mode
The value of the oscillator enable in stop (OSCENINSTOP) bit in the CONFIG (or MOR) register
determines the behavior of the ICG in stop mode. If OSCENINSTOP is low, the ICG is disabled in stop
and, upon execution of the STOP instruction, all ICG activity will cease and the output clocks (CGMXCLK,
CGMOUT, and TBMCLK) will be held low. Power consumption will be minimal.
If OSCENINSTOP is high, the ICG is enabled in stop and activity will continue. This is useful if the
timebase module (TBM) is required to bring the MCU out of stop mode. ICG interrupts will not bring the
MCU out of stop mode in this case.
During STOP, if OSCENINSTOP is low, several functions in the ICG are affected. The stable bits (ECGS
and ICGS) are cleared, which will enable the external clock stabilization divider upon recovery. The clock
monitor is disabled (CMON = 0) which will also clear the clock monitor interrupt enable (CMIE) and clock
monitor flag (CMF) bits. The CS, ICGON, ECGON, N, TRIM, DDIV, and DSTG bits are unaffected.
7.6 CONFIG (or MOR) Register Options
There are four CONFIG (or MOR) register options that affect the functionality of the ICG. These options
are:
• EXTCLKEN (external clock enable)
• EXTXTALEN (external crystal enable)
• EXTSLOW (slow external clock)
• OSCENINSTOP (oscillator enable in stop)
All CONFIG (or MOR) register options will have a default setting.
7.6.1 External Clock Enable (EXTCLKEN)
External clock enable (EXTCLKEN), when set, enables the ECGON bit to be set. ECGON turns on the
external clock input path through the PTB6/(OSC1) pin. When EXTCLKEN is clear, ECGON cannot be
set and PTB6/(OSC1) will always perform the PTB6 function.
The default state for this option is clear.
7.6.2 External Crystal Enable (EXTXTALEN)
External crystal enable (EXTXTALEN), when set, will enable an amplifier to drive the PTB7/(OSC2)/RST
pin from the PTB6/(OSC1) pin. The amplifier will only drive if the external clock enable (EXTCLKEN) bit
and the ECGON bit are also set. If EXTCLKEN or ECGON are clear, PTB7/(OSC2)/RST will perform the
PTB7 function. When EXTXTALEN is clear, PTB7/(OSC2)/RST will always perform the PTB7 function.
EXTXTALEN, when set, also configures the clock monitor to expect an external clock source in the valid
range of crystals (30 kHz to 100 kHz or 1 MHz to 8 MHz). When EXTXTALEN is clear, the clock monitor
will expect an external clock source in the valid range for externally generated clocks when using the clock
monitor (60 Hz to 32 MHz).
EXTXTALEN, when set, also configures the external clock stabilization divider in the clock monitor for a
4096 cycle time-out to allow the proper stabilization time for a crystal. When EXTXTALEN is clear, the
stabilization divider is configured to 16 cycles since an external clock source does not need a start-up
time.
The default state for this option is clear.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
84
Freescale Semiconductor
I/O Registers
7.6.3 Slow External Clock (EXTSLOW)
Slow external clock (EXTSLOW), when set, will decrease the drive strength of the oscillator amplifier,
enabling low-frequency crystal operation (30 kHz–100 kHz) if properly enabled with the external clock
enable (EXTCLKEN) and external crystal enable (EXTXTALEN) bits. When clear, EXTSLOW enables
high-frequency crystal operation (1 MHz to 8 MHz).
EXTSLOW, when set, also configures the clock monitor to expect an external clock source that is slower
than the low-frequency base clock (60 Hz–307.2 kHz). When EXTSLOW is clear, the clock monitor will
expect an external clock faster than the low-frequency base clock (307.2 kHz–32 MHz).
The default state for this option is clear.
7.6.4 Oscillator Enable In Stop (OSCENINSTOP)
Oscillator enable in stop (OSCENINSTOP), when set, will enable the ICG to continue to generate clocks
(either CGMXCLK, CGMOUT, or TBMCLK) in stop mode. This function is used to keep the timebase
running while the rest of the microcontroller stops. When OSCENINSTOP is clear, all clock generation
will cease and CGMXCLK, CGMOUT, and TBMCLK will be forced low during stop.
The default state for this option is clear.
7.7 I/O Registers
The ICG contains five registers, summarized in Figure 7-10. These registers are:
• ICG control register
• ICG multiplier register
• ICG trim register
• ICG DCO divider control register
• ICG DCO stage control register
Several of the bits in these registers have interaction where the state of one bit may force another bit to
a particular state or prevent another bit from being set or cleared. A summary of this interaction is shown
in Table 7-5.
Addr.
Register Name
Bit 7
$0035
ICG Control Register Read:
(ICGCR) Write:
See page 87. Reset:
CMIE
0
6
CMF
0(1)
5
4
3
CMON
CS
ICGON
0
0
1
0
0
0
0
2
ICGS
1
ECGON
Bit 0
ECGS
1. See CMF bit description for method of clearing.
$0037
$0038
ICG Multiplier Register Read:
(ICGMR) Write:
See page 88. Reset:
ICG Trim Register Read:
(ICGTR) Write:
See page 89. Reset:
N6
N5
N4
N3
N2
N1
N0
0
0
0
1
0
1
0
1
TRIM7
TRIM6
TRIM5
TRIM4
TRIM3
TRIM2
TRIM1
TRIM0
0
0
0
0
0
1
= Unimplemented
0
0
R
= Reserved
U = Unaffected
Figure 7-10. ICG Module I/O Register Summary
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
85
Internal Clock Generator Module (ICG)
Addr.
Register Name
Bit 7
ICG DCO Divider Control Read:
$0039
Register (ICGDVR) Write:
See page 89. Reset:
ICG DCO Stage Control Read:
Register (ICGDSR) Write:
See page 89. Reset:
$003A
6
5
4
3
2
1
Bit 0
DDIV3
DDIV2
DDIV1
DDIV0
0
0
0
0
U
U
U
U
DSTG7
DSTG6
DSTG5
DSTG4
DSTG3
DSTG2
DSTG1
DSTG0
R
R
R
R
R
R
R
R
U
U
U
U
U
U
U
U
R
= Reserved
= Unimplemented
U = Unaffected
Figure 7-10. ICG Module I/O Register Summary (Continued)
Table 7-5. ICG Module Register Bit Interaction Summary
Register Bit Results for Given Condition
Condition
CMIE CMF CMON CS ICGON ICGS ECGON ECGS N[6:0] TRIM[7:0] DDIV[3:0] DSTB[7:0]
Reset
0
0
0
0
1
0
0
0
$15
$80
—
—
OSCENINSTOP = 0,
STOP = 1
0
0
0
—
—
0
—
0
—
—
—
—
EXTCLKEN = 0
0
0
0
0
1
—
0
0
—
—
uw
uw
CMF = 1
—
(1)
1
—
1
—
1
—
uw
uw
uw
uw
CMON = 0
0
0
(0)
—
—
—
—
—
—
—
—
—
CMON = 1
—
—
(1)
—
1
—
1
—
uw
uw
uw
uw
CS = 0
—
—
—
(0)
1
—
—
—
—
—
uw
uw
CS = 1
—
—
—
(1)
—
—
1
—
—
—
—
—
ICGON = 0
0
0
0
1
(0)
0
1
—
—
—
—
—
ICGON = 1
—
—
—
—
(1)
—
—
—
—
—
uw
uw
ICGS = 0
us
—
us
uc
—
(0)
—
—
—
—
—
—
ECGON = 0
0
0
0
0
1
—
(0)
0
—
—
uw
uw
ECGS = 0
us
—
us
us
—
—
—
(0)
—
—
—
—
IOFF = 1
—
1*
(1)
1
(1)
0
(1)
—
uw
uw
uw
uw
EOFF = 1
—
1*
(1)
0
(1)
—
(1)
0
uw
uw
uw
uw
N = written
(0)
(0)
(0)
—
—
0*
—
—
—
—
—
—
TRIM = written
(0)
(0)
(0)
—
—
0*
—
—
—
—
—
—
—Register bit is unaffected by the given condition.
0, 1Register bit is forced clear or set (respectively) in the given condition.
0*, 1*Register bit is temporarily forced clear or set (respectively) in the given condition.
(0), (1)Register bit must be clear or set (respectively) for the given condition to occur.
us, uc, uwRegister bit cannot be set, cleared, or written (respectively) in the given condition.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
86
Freescale Semiconductor
I/O Registers
7.7.1 ICG Control Register
The ICG control register (ICGCR) contains the control and status bits for the internal clock generator,
external clock generator, and clock monitor as well as the Clock Select and Interrupt Enable bits.
Address: $0036
Bit 7
Read:
CMIE
Write:
Reset:
0
6
5
4
3
(1)
CMON
CS
ICGON
0
0
0
1
CMF
0
= Unimplemented
2
ICGS
0
1
ECGON
0
Bit 0
ECGS
0
1. See CMF bit description for method of clearing
Figure 7-11. ICG Control Register (ICGCR)
CMIE — Clock Monitor Interrupt Enable Bit
This read/write bit enables clock monitor interrupts. An interrupt will occur when both CMIE and CMF
are set. CMIE can be set when the CMON bit has been set for at least one cycle. CMIE is forced clear
when CMON is clear or during reset.
1 = Clock monitor interrupts enabled
0 = Clock monitor interrupts disabled
CMF — Clock Monitor Interrupt Flag
This read-only bit is set when the clock monitor determines that either ICLK or ECLK becomes inactive
and the CMON bit is set. This bit is cleared by first reading the bit while it is set, followed by writing the
bit low. This bit is forced clear when CMON is clear or during reset.
1 = Either ICLK or ECLK have become inactive
0 = ICLK and ECLK have not become inactive since the last read of the ICGCR, or the clock monitor
is disabled
CMON — Clock Monitor On Bit
This read/write bit enables the clock monitor. CMON can be set when both ICLK and ECLK have been
on and stable for at least one bus cycle (ICGON, ECGON, ICGS, and ECGS are all set). CMON is
forced set when CMF is set, to avoid inadvertent clearing of CMF. CMON is forced clear when either
ICGON or ECGON are clear, during STOP with OSCENINSTOP low, or during reset.
1 = Clock monitor output enabled
0 = Clock monitor output disabled
CS — Clock Select Bit
This read/write bit determines which clock will generate the oscillator output clock (CGMXCLK). This
bit can be set when ECGON and ECGS have been set for at least one bus cycle and can be cleared
when ICGON and ICGS have been set for at least one bus cycle. This bit is forced set when the clock
monitor determines the internal clock (ICLK) is inactive or when ICGON is clear. This bit is forced clear
when the clock monitor determines that the external clock (ECLK) is inactive, when ECGON is clear,
or during reset.
1 = External clock (ECLK) sources CGMXCLK
0 = Internal clock (ICLK) sources CGMXCLK
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
87
Internal Clock Generator Module (ICG)
ICGON — Internal Clock Generator On Bit
This read/write bit enables the internal clock generator. ICGON can be cleared when the CS bit has
been set and the CMON bit has been clear for at least one bus cycle. ICGON is forced set when the
CMON bit is set, the CS bit is clear, or during reset.
1 = Internal clock generator enabled
0 = Internal clock generator disabled
ICGS — Internal Clock Generator Stable Bit
This read-only bit indicates when the internal clock generator has determined that the internal clock
(ICLK) is within about 15% of the desired value. This bit is forced clear when the clock monitor
determines the ICLK is inactive, when ICGON is clear, when the ICG multiplier register (ICGMR) is
written, when the ICG trim register (ICGTR) is written, during STOP with OSCENINSTOP low, or
during reset.
1 = Internal clock is within 15% of the desired value
0 = Internal clock may not be within 15% of the desired value
ECGON — External Clock Generator On Bit
This read/write bit enables the external clock generator. ECGON can be cleared when the CS and
CMON bits have been clear for at least one bus cycle. ECGON is forced set when the CMON bit or the
CS bit is set. ECGON is forced clear during reset.
1 = External clock generator enabled
0 = External clock generator disabled
ECGS — External Clock Generator Stable Bit
This read-only bit indicates when at least 4096 external clock (ECLK) cycles have elapsed since the
external clock generator was enabled. This is not an assurance of the stability of ECLK but is meant
to provide a start-up delay. This bit is forced clear when the clock monitor determines ECLK is inactive,
when ECGON is clear, during STOP with OSCENINSTOP low, or during reset.
1 = 4096 ECLK cycles have elapsed since ECGON was set
0 = External clock is unstable, inactive, or disabled
7.7.2 ICG Multiplier Register
Address: $0037
Bit 7
Read:
Write:
Reset:
0
6
5
4
3
2
1
Bit 0
N6
N5
N4
N3
N2
N1
N0
0
0
1
0
1
0
1
= Unimplemented
Figure 7-12. ICG Multiplier Register (ICGMR)
N6:N0 — ICG Multiplier Factor Bits
These read/write bits change the multiplier used by the internal clock generator. The internal clock
(ICLK) will be (307.2 kHz ± 25%) * N. A value of $00 in this register is interpreted the same as a value
of $01. This register cannot be written when the CMON bit is set. Reset sets this factor to $15 (decimal
21) for default frequency of 6.45 MHz ± 25% (1.613 MHz ± 25% bus).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
88
Freescale Semiconductor
I/O Registers
7.7.3 ICG Trim Register
Address: $0038
Read:
Write:
Bit 7
6
5
4
3
2
1
Bit 0
TRIM7
TRIM6
TRIM5
TRIM4
TRIM3
TRIM2
TRIM1
TRIM0
0
0
0
0
0
0
0
Reset:
1
= Unimplemented
Figure 7-13. ICG Trim Register (ICGTR)
TRIM7:TRIM0 — ICG Trim Factor Bits
These read/write bits change the size of the internal capacitor used by the internal clock generator. By
testing the frequency of the internal clock and incrementing or decrementing this factor accordingly,
the accuracy of the internal clock can be improved to ±2%. Incrementing this register by one decreases
the frequency by 0.195% of the unadjusted value. Decrementing this register by one increases the
frequency by 0.195%. This register cannot be written when the CMON bit is set. Reset sets these bits
to $80, centering the range of possible adjustment.
7.7.4 ICG DCO Divider Register
Address: $0039
Bit 7
6
5
4
Read:
3
2
1
Bit 0
DDIV3
DDIV2
DDIV1
DDIV0
U
U
U
U
Write:
Reset:
0
0
0
0
= Unimplemented
U = Undefined
Figure 7-14. ICG DCO Divider Control Register (ICGDVR)
DDIV3:DDIV0 — ICG DCO Divider Control Bits
These bits indicate the number of divide-by-twos (DDIV) that follow the digitally controlled oscillator.
When ICGON is set, DDIV is controlled by the digital loop filter. The range of valid values for DDIV is
from $0 to $9. Values of $A–$F are interpreted the same as $9. Since the DCO is active during reset,
reset has no effect on DSTG and the value may vary.
7.7.5 ICG DCO Stage Register
Address: $003A
Bit 7
6
5
4
3
2
1
Bit 0
Read:
DSTG7
DSTG6
DSTG5
DSTG4
DSTG3
DSTG2
DSTG1
DSTG0
Write:
R
R
R
R
R
R
R
R
Reset:
U
U
U
U
U
U
U
U
R
= Reserved
= Unimplemented
U = Unaffected
Figure 7-15. ICG DCO Stage Control Register (ICGDSR)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
89
Internal Clock Generator Module (ICG)
DSTG7:DSTG0 — ICG DCO Stage Control Bits
These bits indicate the number of stages (above the minimum) in the digitally controlled oscillator. The
total number of stages is approximately equal to $1FF, so changing DSTG from $00 to $FF will
approximately double the period. Incrementing DSTG will increase the period (decrease the
frequency) by 0.202% to 0.368% (decrementing has the opposite effect). DSTG cannot be written
when ICGON is set to prevent inadvertent frequency shifting. When ICGON is set, DSTG is controlled
by the digital loop filter. Since the DCO is active during reset, reset has no effect on DSTG and the
value may vary.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
90
Freescale Semiconductor
Chapter 8
External Interrupt (IRQ)
8.1 Introduction
The external interrupt (IRQ) module provides a maskable interrupt input.
8.2 Features
Features of the IRQ module include:
• A dedicated external interrupt pin (IRQ1)
• IRQ1 interrupt control bits
• Internal pullup resistor
• Hysteresis buffer
• Programmable edge-only or edge- and level-interrupt sensitivity
• Automatic interrupt acknowledge
8.3 Functional Description
A logic 0 applied to the external interrupt pin can latch a central processor unit (CPU) interrupt request.
Figure 8-2 shows the structure of the IRQ module.
Interrupt signals on the IRQ1 pin are latched into the IRQ1 latch. An interrupt latch remains set until one
of these actions occurs:
• Vector fetch — A vector fetch automatically generates an interrupt acknowledge signal that clears
the latch that caused the vector fetch.
• Software clear — Software can clear an interrupt latch by writing to the appropriate acknowledge
bit in the interrupt status and control register (ISCR). Writing a 1 to the ACK1 bit clears the IRQ1
latch.
• Reset — A reset automatically clears the interrupt latch.
The external interrupt pin is falling-edge triggered and is software- configurable to be both falling-edge
and low-level triggered. The MODE1 bit in the ISCR controls the triggering sensitivity of the IRQ1 pin.
When an interrupt pin is edge-triggered only, the interrupt latch remains set until a vector fetch, software
clear, or reset occurs.
When an interrupt pin is both falling-edge and low-level triggered, the interrupt latch remains set until both
of these occur:
• Vector fetch or software clear
• Return of the interrupt pin to logic 1
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
91
Freescale Semiconductor
SECURITY
MODULE
USER FLASH — 7680 BYTES
COMPUTER OPERATING PROPERLY
MODULE
LOW-VOLTAGE INHIBIT
MODULE
MONITOR ROM — 295 BYTES
2-CHANNEL TIMER INTERFACE
MODULE
USER FLASH VECTOR SPACE — 36 BYTES
FLASH BURN-IN ROM — 1024 BYTES
INTERNAL CLOCK GENERATOR
MODULE
(SOFTWARE SELECTABLE)
KEYBOARD INTERRUPT
MODULE
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATION INTERFACE
MODULE
SYSTEM INTEGRATION
MODULE
IRQ
MODULE
IRQ1(1)
VDD
VSS
PROGRAMMABLE TIME BASE
MODULE
BREAK
MODULE
POWER
Notes:
1. Pin contains integrated pullup resistor
2. High-current source/sink pin
3. Pin contains software selectable pullup resistor if general function I/O pin is configured as input.
Figure 8-1. Block Diagram Highlighting IRQ Block and Pins
DDRA
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
PTA0/KBD0(2), (3)
PTA1/KBD1(2), (3)
PTA2/KBD2/TCH0(2), (3)
PTA3/KBD3/TCH1(2), (3)
PTA4/KBD4(2), (3)
POWER-ON RESET
MODULE
CONTROL AND STATUS REGISTERS — 78 BYTES
USER RAM — 192 BYTES
PTB
ARITHMETIC/LOGIC
UNIT
DDRB
CPU
REGISTERS
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
PTB5/TxD
PTB6/(OSC1)(4)
PTB7/(OSC2)/RST(4)
PTA
M68HC08 CPU
External Interrupt (IRQ)
92
INTERNAL BUS
IRQ1 Pin
INTERNAL ADDRESS BUS
ACK1
TO CPU FOR
BIL/BIH
INSTRUCTIONS
VECTOR
FETCH
DECODER
VDD
INTERNAL
PULLUP
DEVICE
VDD
IRQF1
D
CLR
Q
SYNCHRONIZER
IRQ1
CK
IRQ1
INTERRUPT
REQUEST
IRQ1
LATCH
IMASK1
MODE1
HIGH
VOLTAGE
DETECT
TO MODE
SELECT
LOGIC
Figure 8-2. IRQ Block Diagram
The vector fetch or software clear may occur before or after the interrupt pin returns to logic 1. As long as
the pin is low, the interrupt request remains pending. A reset will clear the latch and the MODE1 control
bit, thereby clearing the interrupt even if the pin stays low.
When set, the IMASK1 bit in the ISCR masks all external interrupt requests. A latched interrupt request
is not presented to the interrupt priority logic unless the IMASK1 bit is clear.
NOTE
The interrupt mask (I) in the condition code register (CCR) masks all
interrupt requests, including external interrupt requests.
8.4 IRQ1 Pin
A logic 0 on the IRQ1 pin can latch an interrupt request into the IRQ1 latch. A vector fetch, software clear,
or reset clears the IRQ1 latch.
If the MODE1 bit is set, the IRQ1 pin is both falling-edge sensitive and low-level sensitive. With MODE1
set, both of the following actions must occur to clear the IRQ1 latch:
• Vector fetch or software clear — A vector fetch generates an interrupt acknowledge signal to clear
the latch. Software may generate the interrupt acknowledge signal by writing a 1 to the ACK1 bit
in the interrupt status and control register (ISCR). The ACK1 bit is useful in applications that poll
the IRQ1 pin and require software to clear the IRQ1 latch. Writing to the ACK1 bit can also prevent
spurious interrupts due to noise. Setting ACK1 does not affect subsequent transitions on the IRQ1
pin. A falling edge on the IRQ1 pin that occurs after writing to the ACK1 bit latches another interrupt
request. If the IRQ1 mask bit, IMASK1, is clear, the CPU loads the program counter with the vector
address at locations $FFFA and $FFFB.
• Return of the IRQ1 pin to logic 1 — As long as the IRQ1 pin is at logic 0, the IRQ1 latch remains
set.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
93
External Interrupt (IRQ)
The vector fetch or software clear and the return of the IRQ1 pin to logic 1 can occur in any order. The
interrupt request remains pending as long as the IRQ1 pin is at logic 0. A reset will clear the latch and the
MODE1 control bit, thereby clearing the interrupt even if the pin stays low.
If the MODE1 bit is clear, the IRQ1 pin is falling-edge sensitive only. With MODE1 clear, a vector fetch or
software clear immediately clears the IRQ1 latch.
The IRQF1 bit in the ISCR can be used to check for pending interrupts. The IRQF1 bit is not affected by
the IMASK1 bit, which makes it useful in applications where polling is preferred.
Use the branch if interrupt pin is high (BIH) or branch if interrupt pin is low (BIL) instruction to read the
logic level on the IRQ1 pin.
NOTE
When using the level-sensitive interrupt trigger, avoid false interrupts by
masking interrupt requests in the interrupt routine.
8.5 IRQ Status and Control Register
The IRQ status and control register (ISCR) controls and monitors operation of the IRQ module. The ISCR
has these functions:
• Shows the state of the IRQ1 interrupt flag
• Clears the IRQ1 interrupt latch
• Masks IRQ1 interrupt request
• Controls triggering sensitivity of the IRQ1 interrupt pin
Address:
$001D
Bit 7
6
5
4
3
2
Read:
0
0
0
0
IRQF1
0
Write:
R
R
R
R
R
ACK1
Reset:
0
0
0
0
U
0
R
= Reserved
1
Bit 0
IMASK1
MODE1
0
0
U = Unaffected
Figure 8-3. IRQ Status and Control Register (ISCR)
IRQF1 — IRQ1 Flag Bit
This read-only status bit is high when the IRQ1 interrupt is pending.
1 = IRQ1 interrupt pending
0 = IRQ1 interrupt not pending
ACK1 — IRQ1 Interrupt Request Acknowledge Bit
Writing a 1 to this write-only bit clears the IRQ1 latch. ACK1 always reads as 0. Reset clears ACK1.
IMASK1 — IRQ1 Interrupt Mask Bit
Writing a 1 to this read/write bit disables IRQ1 interrupt requests. Reset clears IMASK1.
1 = IRQ1 interrupt requests disabled
0 = IRQ1 interrupt requests enabled
MODE1 — IRQ1 Edge/Level Select Bit
This read/write bit controls the triggering sensitivity of the IRQ1 pin. Reset clears MODE1.
1 = IRQ1 interrupt requests on falling edges and low levels
0 = IRQ1 interrupt requests on falling edges only
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
94
Freescale Semiconductor
Chapter 9
Keyboard Interrupt Module (KBI)
9.1 Introduction
The keyboard interrupt module (KBI) provides five independently maskable external interrupt pins.
9.2 Features
KBI features include:
• Five keyboard interrupt pins, on the MC68HC08KX8, are with separate keyboard interrupt enable
bits and one keyboard interrupt mask
• Hysteresis buffers
• Programmable edge-only or edge- and level-interrupt sensitivity
• Automatic interrupt acknowledge
• Exit from low-power modes
INTERNAL BUS
VECTOR FETCH
DECODER
ACKK
KBD0
RESET
VDD
.
.
.
TO PULLUP
ENABLE
KB0IE
KEYF
D
CLR
Q
SYNCHRONIZER
CK
KEYBOARD
INTERRUPT FF
KBD4
or KBD3
TO PULLUP
ENABLE
IMASKK
KEYBOARD
INTERRUPT
REQUEST
MODEK
KB4IE or KB3IE
Figure 9-1. Keyboard Module Block Diagram
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
95
Freescale Semiconductor
SECURITY
MODULE
USER FLASH — 7680 BYTES
COMPUTER OPERATING PROPERLY
MODULE
LOW-VOLTAGE INHIBIT
MODULE
MONITOR ROM — 295 BYTES
2-CHANNEL TIMER INTERFACE
MODULE
USER FLASH VECTOR SPACE — 36 BYTES
FLASH BURN-IN ROM — 1024 BYTES
INTERNAL CLOCK GENERATOR
MODULE
(SOFTWARE SELECTABLE)
KEYBOARD INTERRUPT
MODULE
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATION INTERFACE
MODULE
SYSTEM INTEGRATION
MODULE
IRQ
MODULE
IRQ1(1)
VDD
VSS
PROGRAMMABLE TIME BASE
MODULE
BREAK
MODULE
POWER
Notes:
1. Pin contains integrated pullup resistor
2. High-current source/sink pin
3. Pin contains software selectable pullup resistor if general function I/O pin is configured as input.
Figure 9-2. Block Diagram Highlighting KBI Block and Pins
DDRA
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
PTA0/KBD0(2), (3)
PTA1/KBD1(2), (3)
PTA2/KBD2/TCH0(2), (3)
PTA3/KBD3/TCH1(2), (3)
PTA4/KBD4(2), (3)
POWER-ON RESET
MODULE
CONTROL AND STATUS REGISTERS — 78 BYTES
USER RAM — 192 BYTES
PTB
ARITHMETIC/LOGIC
UNIT
DDRB
CPU
REGISTERS
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
PTB5/TxD
PTB6/(OSC1)(4)
PTB7/(OSC2)/RST(4)
PTA
M68HC08 CPU
Keyboard Interrupt Module (KBI)
96
INTERNAL BUS
Functional Description
Addr.
$001A
$001B
Register Name
Bit 7
6
5
4
3
2
Keyboard Status and Read:
Control Register (KBSCR) Write:
See page 99. Reset:
0
0
0
0
KEYF
0
0
0
0
Keyboard Interrupt Enable Read:
Register (KBIER) Write:
See page 100. Reset:
0
0
0
0
0
ACKK
0
1
Bit 0
IMASKK
MODEK
0
0
0
0
0
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
= Unimplemented
Figure 9-3. I/O Register Summary
9.3 Functional Description
Writing to the KBIE4–KBIE0 bits in the keyboard interrupt enable register independently enables or
disables each port A pin as a keyboard interrupt pin. Enabling a keyboard interrupt pin also enables its
internal pullup device. A logic 0 applied to an enabled keyboard interrupt pin latches a keyboard interrupt
request.
A keyboard interrupt is latched when one or more keyboard pins goes low after all were high. The MODEK
bit in the keyboard status and control register controls the triggering mode of the keyboard interrupt.
• If the keyboard interrupt is edge-sensitive only, a falling edge on a keyboard pin does not latch an
interrupt request if another keyboard pin is already low. To prevent losing an interrupt request on
one pin because another pin is still low, software can disable the latter pin while it is low.
• If the keyboard interrupt is falling edge- and low level-sensitive, an interrupt request is present as
long as any keyboard pin is low.
If the MODEK bit is set, the keyboard interrupt pins are both falling edge- and low level-sensitive, and both
of the following actions must occur to clear a keyboard interrupt request:
• Vector fetch or software clear — A vector fetch generates an interrupt acknowledge signal to clear
the interrupt request. Software may generate the interrupt acknowledge signal by writing a 1 to the
ACKK bit in the keyboard status and control register (KBSCR). The ACKK bit is useful in
applications that poll the keyboard interrupt pins and require software to clear the keyboard
interrupt request. Writing to the ACKK bit prior to leaving an interrupt service routine also can
prevent spurious interrupts due to noise. Setting ACKK does not affect subsequent transitions on
the keyboard interrupt pins. A falling edge that occurs after writing to the ACKK bit latches another
interrupt request. If the keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the program
counter with the vector address at locations $FFE0 and $FFE1.
• Return of all enabled keyboard interrupt pins to logic 1 — As long as any enabled keyboard
interrupt pin is at logic 0, the keyboard interrupt remains set.
The vector fetch or software clear and the return of all enabled keyboard interrupt pins to logic 1 may occur
in any order.
If the MODEK bit is clear, the keyboard interrupt pin is falling edge-sensitive only. With MODEK clear, a
vector fetch or software clear immediately clears the keyboard interrupt request.
Reset clears the keyboard interrupt request and the MODEK bit, clearing the interrupt request even if a
keyboard interrupt pin stays at logic 0.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
97
Keyboard Interrupt Module (KBI)
The keyboard flag bit (KEYF) in the keyboard status and control register can be used to see if a pending
interrupt exists. The KEYF bit is not affected by the keyboard interrupt mask bit (IMASKK) which makes
it useful in applications where polling is preferred.
To determine the logic level on a keyboard interrupt pin, use the data direction register to configure the
pin as an input and read the data register.
NOTE
Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding
keyboard interrupt pin to be an input, overriding the data direction register.
However, the data direction register bit must be a 0 for software to read the
pin.
9.4 Keyboard Initialization
When a keyboard interrupt pin is enabled, the pin may initially be low and cause a false interrupt to occur.
A false interrupt on an edge-triggered pin can be acknowledged immediately after enabling the pin. A false
interrupt on an edge- and level-triggered interrupt pin must be acknowledged after the pin has been pulled
high.
The internal pullup device, the pin capacitance, as well as the external load will factor into the actual
amount of time it takes for the pin to pull high. Considering only an internal pullup of 48 kΩ and pin
capacitance of 8 pF, the pullup time will be on the order of 1 µs.
To prevent a false interrupt on keyboard initialization:
1. Mask keyboard interrupts by setting the IMASKK bit in the keyboard status and control register.
2. Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard interrupt enable register.
3. Write to the ACKK bit in the keyboard status and control register to clear any false interrupts.
4. Clear the IMASKK bit.
Another way to avoid a false interrupt:
1. Configure the keyboard pins as outputs by setting the appropriate DDRA bits in data direction
register A.
2. Write 1s to the appropriate port A data register bits.
3. Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard interrupt enable register.
9.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
9.5.1 Wait Mode
The keyboard module remains active in wait mode. Clearing the IMASKK bit in the keyboard status and
control register enables keyboard interrupt requests to bring the MCU out of wait mode.
9.5.2 Stop Mode
The keyboard module remains active in stop mode. Clearing the IMASKK bit in the keyboard status and
control register enables keyboard interrupt requests to bring the MCU out of stop mode.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
98
Freescale Semiconductor
I/O Registers
9.6 I/O Registers
Two registers control and monitor operation of the keyboard module:
• Keyboard status and control register, KBSCR
• Keyboard interrupt enable register, KBIER
9.6.1 Keyboard Status and Control Register
The keyboard status and control register (KBSCR):
• Flags keyboard interrupt requests
• Acknowledges keyboard interrupt requests
• Masks keyboard interrupt requests
• Controls keyboard interrupt triggering sensitivity
Address: $001A
Read:
Bit 7
6
5
4
3
2
0
0
0
0
KEYF
0
Write:
ACKK
Reset:
0
0
0
0
0
0
1
Bit 0
IMASKK
MODEK
0
0
= Unimplemented
Figure 9-4. Keyboard Status and Control Register (KBSCR)
Bits 7–4 — Not used
These read-only bits always read as 0s.
KEYF — Keyboard Flag Bit
This read-only bit is set when a keyboard interrupt is pending. Reset clears the KEYF bit.
1 = Keyboard interrupt pending
0 = No keyboard interrupt pending
ACKK — Keyboard Acknowledge Bit
Writing a 1 to this write-only bit clears the keyboard interrupt request. ACKK always reads as 0. Reset
clears ACKK.
IMASKK — Keyboard Interrupt Mask Bit
Writing a 1 to this read/write bit prevents the output of the keyboard interrupt mask from generating
interrupt requests. Reset clears the IMASKK bit.
1 = Keyboard interrupt requests masked
0 = Keyboard interrupt requests not masked
MODEK — Keyboard Triggering Sensitivity Bit
This read/write bit controls the triggering sensitivity of the keyboard interrupt pins. Reset clears
MODEK.
1 = Keyboard interrupt requests on falling edges and low levels
0 = Keyboard interrupt requests on falling edges only
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
99
Keyboard Interrupt Module (KBI)
9.6.2 Keyboard Interrupt Enable Register
The keyboard interrupt enable register (KBIER) enables or disables each port A pin to operate as a
keyboard interrupt pin.
Address: $001B
Read:
Bit 7
6
5
0
0
0
0
0
0
Write:
Reset:
4
3
2
1
Bit 0
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
= Unimplemented
Figure 9-5. Keyboard Interrupt Enable Register (KBIER)
KBIE4–KBIE0 — Keyboard Interrupt Enable Bits
Each of these read/write bits enables the corresponding keyboard interrupt pin to latch interrupt
requests. Reset clears the keyboard interrupt enable register.
1 = PAx pin enabled as keyboard interrupt pin
0 = PAx pin not enabled as keyboard interrupt pin
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
100
Freescale Semiconductor
Chapter 10
Low-Voltage Inhibit (LVI)
10.1 Introduction
This section describes the low-voltage inhibit (LVI) module, which monitors the voltage on the VDD pin
and can force a reset when the VDD voltage falls below the LVI trip falling voltage, VTRIPF.
10.2 Features
Features of the LVI module include:
• Programmable LVI reset
• Programmable power consumption
• Selectable LVI trip voltage
• Programmable stop mode operation
10.3 Functional Description
Figure 10-1 shows the structure of the LVI module. LVISTOP, LVIPWRD, LVI5OR3, and LVIRSTD are
user selectable options found in the configuration register (CONFIG1). See Chapter 4 Configuration
Register (CONFIG).
VDD
STOP INSTRUCTION
LVISTOP
FROM CONFIG
FROM CONFIG
LVIRSTD
LVIPWRD
FROM CONFIG
LOW VDD
DETECTOR
VDD > LVITRIP = 0
LVI RESET
VDD ≤ LVITRIP = 1
LVIOUT
LVI5OR3
FROM CONFIG
Figure 10-1. LVI Module Block Diagram
The LVI is enabled out of reset. The LVI module contains a bandgap reference circuit and comparator.
Clearing the LVI power disable bit, LVIPWRD, enables the LVI to monitor VDD voltage. Clearing the LVI
reset disable bit, LVIRSTD, enables the LVI module to generate a reset when VDD falls below a voltage,
VTRIPF. Setting the LVI enable in stop mode bit, LVISTOP, enables the LVI to operate in stop mode.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
101
Low-Voltage Inhibit (LVI)
Setting the LVI 5-V or 3-V trip point bit, LVI5OR3, enables the trip point voltage, VTRIPF, to be configured
for 5-V operation. Clearing the LVI5OR3 bit enables the trip point voltage, VTRIPF, to be configured for 3-V
operation. The actual trip thresholds are specified in 17.5 5.0-Vdc DC Electrical Characteristics and .
NOTE
After a power-on reset, the LVI’s default mode of operation is 3 volts. If a
5-V system is used, the user must set the LVI5OR3 bit to raise the trip point
to 5-V operation.
If the user requires 5-V mode and sets the LVI5OR3 bit after power-on reset
while the VDD supply is not above the VTRIPR for 5-V mode, the MCU will
immediately go into reset. The next time the LVI releases the reset, the
supply will be above the VTRIPR for 5-V mode.
Once an LVI reset occurs, the MCU remains in reset until VDD rises above a voltage, VTRIPR, which
causes the MCU to exit reset. See Chapter 13 System Integration Module (SIM) for the reset recovery
sequence.
The output of the comparator controls the state of the LVIOUT flag in the LVI status register (LVISR) and
can be used for polling LVI operation when the LVI reset is disabled.
10.3.1 Polled LVI Operation
In applications that can operate at VDD levels below the VTRIPF level, software can monitor VDD by polling
the LVIOUT bit. In the configuration register, the LVIPWRD bit must be at 0 to enable the LVI module, and
the LVIRSTD bit must be at 1 to disable LVI resets.
10.3.2 Forced Reset Operation
In applications that require VDD to remain above the VTRIPF level, enabling LVI resets allows the LVI
module to reset the MCU when VDD falls below the VTRIPF level. In the configuration register, the
LVIPWRD and LVIRSTD bits must be at 0 to enable the LVI module and to enable LVI resets.
10.3.3 Voltage Hysteresis Protection
Once the LVI has triggered (by having VDD fall below VTRIPF), the LVI will maintain a reset condition until
VDD rises above the rising trip point voltage, VTRIPR. This prevents a condition in which the MCU is
continually entering and exiting reset if VDD is approximately equal to VTRIPF. VTRIPR is greater than
VTRIPF by the hysteresis voltage, VHYS.
10.3.4 LVI Trip Selection
The LVI5OR3 bit in the configuration register selects whether the LVI is configured for 5-V or 3-V
protection.
NOTE
The microcontroller is guaranteed to operate at a minimum supply voltage.
The trip point (VTRIPF [5 V] or VTRIPF [3 V]) may be lower than this. See 17.5
5.0-Vdc DC Electrical Characteristics and for the actual trip point voltages.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
102
Freescale Semiconductor
LVI Status Register
10.4 LVI Status Register
The LVI status register (LVISR) indicates if the VDD voltage was detected below the VTRIPF level while LVI
resets have been disabled.
Address: $FE0C
Read:
Bit 7
6
5
4
3
2
1
Bit 0
LVIOUT
0
0
0
0
0
0
R
0
0
0
0
0
0
0
0
R
= Reserved
Write:
Reset:
= Unimplemented
Figure 10-2. LVI Status Register (LVISR)
LVIOUT — LVI Output Bit
This read-only flag becomes set when the VDD voltage falls below the VTRIPF trip voltage and is cleared
when VDD voltage rises above VTRIPR. The difference in these threshold levels results in a hysteresis
that prevents oscillation into and out of reset. (See Table 10-1.) Reset clears the LVIOUT bit.
Table 10-1. LVIOUT Bit Indication
VDD
LVIOUT
VDD > VTRIPR
0
VDD < VTRIPF
1
VTRIPF < VDD < VTRIPR
Previous value
10.5 LVI Interrupts
The LVI module does not generate interrupt requests.
10.6 Low-Power Modes
The STOP and WAIT instructions put the MCU in low power-consumption standby modes.
10.6.1 Wait Mode
If enabled, the LVI module remains active in wait mode. If enabled to generate resets, the LVI module can
generate a reset and bring the MCU out of wait mode.
10.6.2 Stop Mode
When the LVIPWRD bit in the configuration register is cleared and the LVISTOP bit in the configuration
register is set, the LVI module remains active in stop mode. If enabled to generate resets, the LVI module
can generate a reset and bring the MCU out of stop mode.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
103
Low-Voltage Inhibit (LVI)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
104
Freescale Semiconductor
Chapter 11
Input/Output (I/O) Ports (PORTS)
11.1 Introduction
Thirteen bidirectional input/output (I/O) pins form two parallel ports in the 16-pin plastic dual in-line
package (PDIP) and small outline integrated circuit (SOIC) package in the MC68HC908KX8 part. All I/O
pins are programmable as inputs or outputs. Port A has software selectable pullup resistors if the port is
used as a general-function input port.
NOTE
Connect any unused I/O pins to an appropriate logic level, either VDD or VSS.
Although the I/O ports do not require termination for proper operation,
termination reduces excess current consumption and the possibility of
electrostatic damage.
See Figure 11-1 for a summary of the I/O port registers.
Addr.
$0000
$0001
Register Name
Port A Data Register Read:
(PTA) Write:
See page 106. Reset:
Port B Data Register Read:
(PTB) Write:
See page 108. Reset:
$0004
Data Direction Register A Read:
(DDRA) Write:
See page 106. Reset:
$0005
Data Direction Register B Read:
(DDRB) Write:
See page 109. Reset:
$000D
Port A Input Pullup Enable Read:
Register (PTAPUE) Write:
See page 108. Reset:
Bit 7
6
5
0
0
0
4
3
2
1
Bit 0
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
Unaffected by reset
PTB7
PTB6
PTB5
PTB4
PTB3
Unaffected by reset
0
0
0
0
0
DDRB7
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
0
0
0
0
PTAPUE4
PTAPUE3
PTAPUE2
PTAPUE1
PTAPUE0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 11-1. I/O Port Register Summary
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
105
Input/Output (I/O) Ports (PORTS)
11.2 Port A
Port A is a 5-bit special function port on the MC68HC908KX8 that shares all of its pins with the keyboard
interrupt module (KBI) and the 2-channel timer. Port A contains software programmable pullup resistors
enabled when a port pin is used as a general-function input. Port A pins are also high-current port pins
with 15-mA source/15-mA sink capabilities.
11.2.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the five port A pins.
Address:
$0000
Bit 7
6
5
0
0
0
Read:
Write:
Reset:
4
3
2
1
Bit 0
PTA4
PTA3
PTA2
PTA1
PTA0
KBD1
KBD0
Unaffected by reset
Alternate Function:
KBD4
KBD3
KBD2
Alternate Function:
VREFH
TCH1
TCH0
= Unimplemented
Figure 11-2. Port A Data Register (PTA)
PTA4–PTA0 — Port A Data Bits
These read/write bits are software programmable. Data direction of each port A pin is under the control
of the corresponding bit in data direction register A. Reset has no effect on port A data.
KBD4–KBD0 — Keyboard Wakeup Bits
The keyboard interrupt enable bits, KBIE4–KBIE0, in the keyboard interrupt control register, enable
the port A pins as external interrupt pins. See Chapter 9 Keyboard Interrupt Module (KBI).
TCH1 and TCH0 — Timer Channel I/O Bits
The PTA3/KBD3/TCH1 and PTA2/KBD2/TCH0 pins are the TIM input capture/output compare pins.
The edge/level select bits, ELSxB and ELSxA, determine whether the pins are timer channel I/O pins
or general-purpose I/O pins. See Chapter 9 Keyboard Interrupt Module (KBI).
11.2.2 Data Direction Register A
Data direction register A (DDRA) determines whether each port A pin is an input or an output. Writing a 1
to a DDRA bit enables the output buffer for the corresponding port A pin; a 0 disables the output buffer.
Address: $0004
Read:
Bit 7
6
5
0
0
0
0
0
0
Write:
Reset:
4
3
2
1
Bit 0
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
= Unimplemented
Figure 11-3. Data Direction Register A (DDRA)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
106
Freescale Semiconductor
Port A
DDRA4–DDRA0 — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears DDRA4–DDRA0, configuring all port
A pins as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
NOTE
Avoid glitches on port A pins by writing to the port A data register before
changing data direction register A bits from 0 to 1.
Figure 11-4 shows the port A I/O logic.
READ DDRA ($0004)
INTERNAL DATA BUS
WRITE DDRA ($0004)
DDRAx
RESET
WRITE PTA ($0000)
PTAx
PTAx
VDD
PTAPUEx
INTERNAL
PULLUP
DEVICE
READ PTA ($0000)
Figure 11-4. Port A I/O Circuit
When bit DDRAx is a 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a 0,
reading address $0000 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 11-1 summarizes the operation of the port A pins.
Table 11-1. Port A Pin Functions
PTAPUE
Bit
DDRA
Bit
PTA
Bit
I/O Pin
Mode
Accesses to DDRA
VDD(1)
Accesses to PTA
Read/Write
Read
Write
DDRA4–DDRA0
Pin
PTA4–PTA0(2)
1
0
X
0
0
X
Input, Hi-Z
DDRA4–DDRA0
Pin
PTA4–PTA0(3)
X
1
X
Output
DDRA4–DDRA0
PTA4–PTA0
PTA4–PTA0
Input,
X = Don’t care
Hi-Z = High impedance
1. I/O pin pulled up to VDD by internal pulllup device
2. Writing affects data register, but does not affect input.
11.2.3 Port A Input Pullup Enable Register
The port A input pullup enable register (PTAPUE) contains a software configurable pullup device for each
of the five port A pins. Each bit is individually configurable and requires that the data direction register,
DDRA, bit be configured as an input. Each pullup is automatically disabled when a port bit’s DDRA is
configured for output mode.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
107
Input/Output (I/O) Ports (PORTS)
Address:
Read:
$000D
Bit 7
6
5
0
0
0
0
0
Write:
Reset:
0
4
3
2
1
Bit 0
PTAPUE4
PTAPUE3
PTAPUE2
PTAPUE1
PTAPUE0
0
0
0
0
0
= Unimplemented
Figure 11-5. Port A Input Pullup Enable Register (PTAPUE)
PTAPUE4–PTAPUE0 — Port A Input Pullup Enable Bits
These writable bits are software programmable to enable pullup devices on an input port bit.
1 = Corresponding port A pin configured to have internal pullup
0 = Corresponding port A pin has internal pullup disconnected
11.3 Port B
Port B is an 8-bit special-function port that shares four of its pins with the analog-to-digital converter
module (ADC), two with the serial communication interface module (SCI) and two with an optional
external clock source.
11.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the eight port B pins.
Address:
Read:
Write:
$0001
Bit 7
6
5
4
3
2
1
Bit 0
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
AD2
AD1
AD0
Reset:
Alternate
Function:
Unaffected by reset
OSC2
OSC1
TxD
RxD
AD3
Figure 11-6. Port B Data Register (PTB)
PTB7–PTB0 — Port B Data Bits
These read/write bits are software-programmable. Data direction of each port B pin is under the control
of the corresponding bit in data direction register B. Reset has no effect on port B data.
OSC2 and OSC1 — OSC2 and OSC1 Bits
Under software control, PTB7 and PTB6 can be configured as external clock inputs and outputs. PTB7
will become an output clock, OSC2, if selected in the configuration registers and enabled in the ICG
registers. PTB6 will become an external input clock source, OSC1, if selected in the configuration
registers and enabled in the ICG registers. See Chapter 7 Internal Clock Generator Module (ICG) and
Chapter 4 Configuration Register (CONFIG).
RxD — SCI Receive Data Input Bit
The PTB1/RxD pin is the receive data input for the SCI module. When the enable SCI bit, ENSCI, is
clear, the SCI module is disabled, and the PTB1/RxD pin is available for general-purpose I/O. See
Chapter 12 Serial Communications Interface Module (SCI).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
108
Freescale Semiconductor
Port B
TxD — SCI Transmit Data Output Bit
The PTB0/TxD pin is the transmit data output for the SCI module. When the enable SCI bit, ENSCI, is
clear, the SCI module is disabled, and the PTB0/TxD pin is available for general-purpose I/O. See
Chapter 12 Serial Communications Interface Module (SCI).
AD3–AD0 — Analog-to-Digital Input Bits
AD3–AD0 are pins used for the input channels to the analog-to-digital converter (ADC) module. The
channel select bits in the ADC status and control register define which port B pin will be used as an
ADC input and overrides any control from the port I/O logic by forcing that pin as the input to the analog
circuitry. See Chapter 3 Analog-to-Digital Converter (ADC).
11.3.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is an input or an output. Writing a 1
to a DDRB bit enables the output buffer for the corresponding port B pin; a 0 disables the output buffer.
Address: $0005
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
DDRB7
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
0
Figure 11-7. Data Direction Register B (DDRB)
DDRB7–DDRB0 — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears DDRB7–DDRB0, configuring all port
B pins as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE
Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1.
Figure 11-8 shows the port B I/O logic.
READ DDRB ($0005)
INTERNAL DATA BUS
WRITE DDRB ($0005)
RESET
DDRBx
WRITE PTB ($0001)
PTBx
PTBx
READ PTB ($0001)
Figure 11-8. Port B I/O Circuit
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
109
Input/Output (I/O) Ports (PORTS)
When bit DDRBx is a 1, reading address $0001 reads the PTBx data latch. When bit DDRBx is a 0,
reading address $0001 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 11-2 summarizes the operation of the port B pins.
Table 11-2. Port B Pin Functions
DDRB
Bit
PTB
Bit
I/O Pin
Mode
Accesses to DDRB
Read/Write
Read
Accesses to PTB
Write
0
X
Input, Hi-Z
DDRB7–DDRB0
Pin
PTB7–PTB0(1)
1
X
Output
DDRB7–DDRB0
PTB7–PTB0
PTB7–PTB0
X = Don’t care
Hi-Z = High impedance
1. Writing affects data register, but does not affect input.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
110
Freescale Semiconductor
Chapter 12
Serial Communications Interface Module (SCI)
12.1 Introduction
The serial communications interface (SCI) allows asynchronous communications with peripheral devices
and other microcontroller unit (MCU).
12.2 Features
The SCI module’s features include:
• Full-duplex operation
• Standard mark/space non-return-to-zero (NRZ) format
• Choice of baud rate clock source:
– Internal bus clock
– CGMXCLK
• 32 programmable baud rates
• Programmable 8-bit or 9-bit character length
• Separately enabled transmitter and receiver
• Separate receiver and transmitter central processor unit (CPU) interrupt requests
• Programmable transmitter output polarity
• Two receiver wakeup methods:
– Idle line wakeup
– Address mark wakeup
• Interrupt-driven operation with eight interrupt flags:
– Transmitter empty
– Transmission complete
– Receiver full
– Idle receiver input
– Receiver overrun
– Noise error
– Framing error
– Parity error
• Receiver framing error detection
• Hardware parity checking
• 1/16 bit-time noise detection
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
111
Freescale Semiconductor
SECURITY
MODULE
USER FLASH — 7680 BYTES
COMPUTER OPERATING PROPERLY
MODULE
LOW-VOLTAGE INHIBIT
MODULE
MONITOR ROM — 295 BYTES
2-CHANNEL TIMER INTERFACE
MODULE
USER FLASH VECTOR SPACE — 36 BYTES
FLASH BURN-IN ROM — 1024 BYTES
INTERNAL CLOCK GENERATOR
MODULE
(SOFTWARE SELECTABLE)
KEYBOARD INTERRUPT
MODULE
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATION INTERFACE
MODULE
SYSTEM INTEGRATION
MODULE
IRQ
MODULE
IRQ1(1)
VDD
VSS
PROGRAMMABLE TIME BASE
MODULE
BREAK
MODULE
POWER
Notes:
1. Pin contains integrated pullup resistor
2. High-current source/sink pin
3. Pin contains software selectable pullup resistor if general function I/O pin is configured as input.
Figure 12-1. Block Diagram Highlighting SCI Block and Pins
DDRA
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
PTA0/KBD0(2), (3)
PTA1/KBD1(2), (3)
PTA2/KBD2/TCH0(2), (3)
PTA3/KBD3/TCH1(2), (3)
PTA4/KBD4(2), (3)
POWER-ON RESET
MODULE
CONTROL AND STATUS REGISTERS — 78 BYTES
USER RAM — 192 BYTES
PTB
ARITHMETIC/LOGIC
UNIT
DDRB
CPU
REGISTERS
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
PTB5/TxD
PTB6/(OSC1)(4)
PTB7/(OSC2)/RST(4)
PTA
M68HC08 CPU
Serial Communications Interface Module (SCI)
112
INTERNAL BUS
Pin Name Conventions
12.3 Pin Name Conventions
The generic names of the SCI input/output (I/O) pins are:
• RxD, receive data
• TxD, transmit data
SCI I/O lines are implemented by sharing parallel I/O port pins. The full name of an SCI input or output
reflects the name of the shared port pin. Table 12-1 shows the full names and the generic names of the
SCI I/O pins.The generic pin names appear in the text of this section.
Table 12-1. Pin Name Conventions
Generic Pin
Names
Full Pin Names
RxD
TxD
PTB4/RxD
PTB5/TxD
12.4 Functional Description
Figure 12-3 shows the structure of the SCI module. The SCI allows full-duplex, asynchronous, NRZ serial
communication between the MCU and remote devices, including other MCUs. The transmitter and
receiver of the SCI operate independently, although they use the same baud rate generator.
The source of the baud rate clock is determined by the configuration register 2 bit, SCIBDSRC. If
SCIBDSRC is set then the source of the SCI is the internal data bus clock. If SCIBDSRC is cleared, the
source of the SCI is oscillator output CGMXCLK.
During normal operation, the CPU monitors the status of the SCI, writes the data to be transmitted, and
processes received data.
12.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 12-2.
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
PARITY
OR DATA
BIT
BIT 6
9-BIT DATA FORMAT
BIT M IN SCC1 SET
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
NEXT
START
BIT
PARITY
OR DATA
BIT
BIT 7
BIT 8 STOP
BIT
NEXT
START
BIT
Figure 12-2. SCI Data Formats
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
113
Serial Communications Interface Module (SCI)
INTERNAL BUS
ERROR
INTERRUPT
CONTROL
RECEIVE
SHIFT REGISTER
RxD
SCI DATA
REGISTER
RECEIVER
INTERRUPT
CONTROL
TRANSMITTER
INTERRUPT
CONTROL
SCI DATA
REGISTER
TRANSMIT
SHIFT REGISTER
TxD
TXINV
SCTIE
R8
TCIE
T8
SCRIE
ILIE
TE
SCTE
RE
TC
RWU
SBK
SCRF
OR
ORIE
IDLE
NF
NEIE
FE
FEIE
PE
PEIE
LOOPS
LOOPS
WAKEUP
CONTROL
RECEIVE
CONTROL
ENSCI
ENSCI
TRANSMIT
CONTROL
FLAG
CONTROL
BKF
M
RPF
WAKE
ILTY
BAUDCLK
÷4
CGMXCLK
A
BUSCLK
B
PRESCALER
BAUD RATE
GENERATOR
÷ 16
PEN
PTY
DATA SELECTION
CONTROL
S
SCIBDSRC
Figure 12-3. SCI Module Block Diagram
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
114
Freescale Semiconductor
Functional Description
Addr.
Register Name
$0013
SCI Control Register 1
(SCC1)
See page 125.
$0014
SCI Control Register 2
(SCC2)
See page 127.
$0015
$0016
SCI Control Register 3
(SCC3)
See page 129.
SCI Status Register 1
(SCS1)
See page 130.
$0017
SCI Status Register 2
(SCS2)
See page 132.
$0018
SCI Data Register
(SCDR)
See page 133.
$0019
SCI Baud Rate Register
(SCBR)
See page 133.
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
LOOPS
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
R8
0
0
0
0
0
0
0
T8
R
R
ORIE
NEIE
FEIE
PEIE
U
SCTE
U
TC
0
SCRF
0
IDLE
0
OR
0
NF
0
FE
0
PE
1
0
1
0
0
0
0
0
0
0
0
0
0
BKF
0
RPF
0
R7
T7
0
R6
T6
0
R5
T5
0
R2
T2
0
R1
T1
0
R0
T0
0
0
SCR1
SCR0
0
SCP1
0
0
= Unimplemented
0
0
R4
R3
T4
T3
Unaffected by reset
SCP0
R
SCR2
0
R
0
= Reserved
0
0
U = Unaffected
0
Figure 12-4. SCI I/O Register Summary
12.4.2 Transmitter
Figure 12-5 shows the structure of the SCI transmitter.
12.4.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1
(SCC1) determines character length. When transmitting 9-bit data, bit T8 in SCI control register 3 (SCC3)
is the ninth bit (bit 8).
12.4.2.2 Character Transmission
During an SCI transmission, the transmit shift register shifts a character out to the TxD pin. The SCI data
register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register. To
initiate an SCI transmission:
1. Enable the SCI by writing a 1 to the enable SCI bit (ENSCI) in SCI control register 1 (SCC1).
2. Enable the transmitter by writing a 1 to the transmitter enable bit (TE) in SCI control register 2
(SCC2).
3. Clear the SCI transmitter empty bit by first reading SCI status register 1 (SCS1) and then writing
to the SCDR.
4. Repeat step 3 for each subsequent transmission.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
115
Serial Communications Interface Module (SCI)
INTERNAL BUS
÷ 16
SCI DATA REGISTER
SCP1
11-BIT
TRANSMIT
SHIFT REGISTER
STOP
BAUDCLK
BAUD
DIVIDER
SCP0
SCR1
H
SCR2
8
7
6
5
4
3
2
START
PRESCALER
÷4
1
0
L
TxD
MSB
SCR0
PARITY
GENERATION
T8
BREAK
ALL 0s
PTY
PREAMBLE
ALL 1s
PEN
SHIFT ENABLE
M
LOAD FROM SCDR
TRANSMITTER CPU INTERRUPT REQUEST
TXINV
TRANSMITTER
CONTROL LOGIC
SCTE
SCTE
SCTIE
TC
TCIE
SBK
LOOPS
SCTIE
ENSCI
TC
TE
TCIE
Figure 12-5. SCI Transmitter Break Characters
At the start of a transmission, transmitter control logic automatically loads the transmit shift register with
a preamble of logic 1s. After the preamble shifts out, control logic transfers the SCDR data into the
transmit shift register. A logic 0 start bit automatically goes into the least significant bit position of the
transmit shift register. A logic 1 stop bit goes into the most significant bit position.
The SCI transmitter empty bit, SCTE, in SCS1 becomes set when the SCDR transfers a byte to the
transmit shift register. The SCTE bit indicates that the SCDR can accept new data from the internal data
bus. If the SCI transmit interrupt enable bit, SCTIE, in SCC2 is also set, the SCTE bit generates a
transmitter CPU interrupt request.
When the transmit shift register is not transmitting a character, the TxD pin goes to the idle condition,
logic 1. If at any time software clears the ENSCI bit in SCI control register 1 (SCC1), the transmitter and
receiver relinquish control of the port B pins.
Writing a 1 to the send break bit, SBK, in SCC2 loads the transmit shift register with a break character. A
break character contains all logic 0s and has no start, stop, or parity bit. Break character length depends
on the M bit in SCC1. As long as SBK is at 1, transmitter logic continuously loads break characters into
the transmit shift register. After software clears the SBK bit, the shift register finishes transmitting the last
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
116
Freescale Semiconductor
Functional Description
break character and then transmits at least one 1. The automatic 1 at the end of a break character
guarantees the recognition of the start bit of the next character.
12.4.2.3 Break Characters
The SCI recognizes a break character when a start bit is followed by eight or nine 0 data bits and a 0
where the stop bit should be. Receiving a break character has these effects on SCI registers:
• Sets the framing error bit (FE) in SCS1
• Sets the SCI receiver full bit (SCRF) in SCS1
• Clears the SCI data register (SCDR)
• Clears the R8 bit in SCC3
• Sets the break flag bit (BKF) in SCS2
• May set the overrun (OR), noise flag (NF), parity error (PE), or reception-in-progress flag (RPF) bits
12.4.2.4 Idle Characters
An idle character contains all 1s and has no start, stop, or parity bit. Idle character length depends on the
M bit in SCC1. The preamble is a synchronizing idle character that begins every transmission.
If the TE bit is cleared during a transmission, the TxD pin becomes idle after completion of the
transmission in progress. Clearing and then setting the TE bit during a transmission queues an idle
character to be sent after the character currently being transmitted.
NOTE
When queueing an idle character, return the TE bit to 1 before the stop bit
of the current character shifts out to the TxD pin. Setting TE after the stop
bit appears on TxD causes data previously written to the SCDR to be lost.
A good time to toggle the TE bit for a queued idle character is when the
SCTE bit becomes set and just before writing the next byte to the SCDR.
12.4.2.5 Inversion of Transmitted Output
The transmit inversion bit (TXINV) in SCI control register 1 (SCC1) reverses the polarity of transmitted
data. All transmitted values, including idle, break, start, and stop bits, are inverted when TXINV is at 1.
See 12.7.1 SCI Control Register 1.
12.4.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the SCI transmitter:
• SCI transmitter empty (SCTE) — The SCTE bit in SCS1 indicates that the SCDR has transferred
a character to the transmit shift register. SCTE can generate a transmitter CPU interrupt request.
Setting the SCI transmit interrupt enable bit, SCTIE, in SCC2 enables the SCTE bit to generate
transmitter CPU interrupt requests.
• Transmission complete (TC) — The TC bit in SCS1 indicates that the transmit shift register and the
SCDR are empty and that no break or idle character has been generated. The transmission
complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to generate transmitter CPU
interrupt requests.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
117
Serial Communications Interface Module (SCI)
12.4.3 Receiver
Figure 12-6 shows the structure of the SCI receiver.
INTERNAL BUS
SCR1
SCR2
SCP0
SCR0
BAUD
DIVIDER
÷ 16
DATA
RECOVERY
RxD
CPU INTERRUPT REQUEST
11-BIT
RECEIVE SHIFT REGISTER
8
7
6
5
M
WAKE
ILTY
PEN
PTY
4
3
2
1
0
L
ALL 0s
RPF
ERROR CPU INTERRUPT REQUEST
H
ALL 1s
BKF
STOP
PRESCALER
MSB
÷4
BAUDCLK
SCI DATA REGISTER
START
SCP1
RWU
SCRF
WAKEUP
LOGIC
PARITY
CHECKING
IDLE
ILIE
SCRF
SCRIE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
IDLE
R8
ILIE
SCRIE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
Figure 12-6. SCI Receiver Block Diagram
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
118
Freescale Semiconductor
Functional Description
12.4.3.1 Character Length
The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1
(SCC1) determines character length. When receiving 9-bit data, bit R8 in SCI control register 2 (SCC2)
is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7).
12.4.3.2 Character Reception
During an SCI reception, the receive shift register shifts characters in from the RxD pin. The SCI data
register (SCDR) is the read-only buffer between the internal data bus and the receive shift register.
After a complete character shifts into the receive shift register, the data portion of the character transfers
to the SCDR. The SCI receiver full bit, SCRF, in SCI status register 1 (SCS1) becomes set, indicating that
the received byte can be read. If the SCI receive interrupt enable bit, SCRIE, in SCC2 is also set, the
SCRF bit generates a receiver CPU interrupt request.
12.4.3.3 Data Sampling
The receiver samples the RxD pin at the RT clock rate. The RT clock is an internal signal with a frequency
16 times the baud rate. To adjust for baud rate mismatch, the RT clock is resynchronized at these times
(see Figure 12-7):
• After every start bit
• After the receiver detects a data bit change from 1 to 0 (after the majority of data bit samples at
RT8, RT9, and RT10 returns a valid 1 and the majority of the next RT8, RT9, and RT10 samples
returns a valid 0)
To locate the start bit, data recovery logic does an asynchronous search for a 0 preceded by three 1s.
When the falling edge of a possible start bit occurs, the RT clock begins to count to 16.
START BIT
RxD
SAMPLES
START BIT
QUALIFICATION
LSB
START BIT
DATA
VERIFICATION SAMPLING
RT CLOCK
STATE
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RT10
RT11
RT12
RT13
RT14
RT15
RT16
RT1
RT2
RT3
RT4
RT
CLOCK
RT CLOCK
RESET
Figure 12-7. Receiver Data Sampling
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
119
Serial Communications Interface Module (SCI)
To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7.
Table 12-2 summarizes the results of the start bit verification samples.
Table 12-2. Start Bit Verification
RT3, RT5,
and RT7 Samples
Start Bit
Verification
Noise Flag
000
Yes
0
001
Yes
1
010
Yes
1
011
No
0
100
Yes
1
101
No
0
110
No
0
111
No
0
If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins.
To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and
RT10. Table 12-3 summarizes the results of the data bit samples.
Table 12-3. Data Bit Recovery
RT8, RT9,
and RT10 Samples
Data Bit
Determination
Noise Flag
000
0
0
001
0
1
010
0
1
011
1
1
100
0
1
101
1
1
110
1
1
111
1
0
NOTE
The RT8, RT9, and RT10 samples do not affect start bit verification. If any
or all of the RT8, RT9, and RT10 start bit samples are 1s following a
successful start bit verification, the noise flag (NF) is set and the receiver
assumes that the bit is a start bit.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
120
Freescale Semiconductor
Functional Description
To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 12-4
summarizes the results of the stop bit samples.
Table 12-4. Stop Bit Recovery
RT8, RT9,
and RT10 Samples
Framing
Error Flag
Noise Flag
000
1
0
001
1
1
010
1
1
011
0
1
100
1
1
101
0
1
110
0
1
111
0
0
12.4.3.4 Framing Errors
If the data recovery logic does not detect a 1 where the stop bit should be in an incoming character, it sets
the framing error bit, FE, in SCS1. A break character also sets the FE bit because a break character has
no stop bit. The FE bit is set at the same time that the SCRF bit is set.
12.4.3.5 Baud Rate Tolerance
A transmitting device may be operating at a baud rate below or above the receiver baud rate.
Accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the
actual stop bit. Then a noise error occurs. If more than one of the samples is outside the stop bit, a framing
error occurs. In most applications, the baud rate tolerance is much more than the degree of misalignment
that is likely to occur.
As the receiver samples an incoming character, it resynchronizes the RT clock on any valid falling edge
within the character. Resynchronization within characters corrects misalignments between transmitter bit
times and receiver bit times.
Slow Data Tolerance
Figure 12-8 shows how much a slow received character can be misaligned without causing a noise
error or a framing error. The slow stop bit begins at RT8 instead of RT1 but arrives in time for the stop
bit data samples at RT8, RT9, and RT10.
MSB
STOP
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RECEIVER
RT CLOCK
DATA
SAMPLES
Figure 12-8. Slow Data
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
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Serial Communications Interface Module (SCI)
With the misaligned character shown in Figure 12-8, the receiver counts 154 RT cycles at the point
when the count of the transmitting device is 9 bit times × 16 RT cycles + 3 RT cycles = 147 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a slow 8-bit
character with no errors is
154 – 147
-------------------------- × 100 = 4.54%
154
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 12-8, the receiver counts 170 RT cycles at the point
when the count of the transmitting device is
10 bit times × 16 RT cycles + 3 RT cycles = 163 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit
character with no errors is
170 – 163 × 100 = 4.12%
-------------------------170
Fast Data Tolerance
Figure 12-9 shows how much a fast received character can be misaligned without causing a noise
error or a framing error. The fast stop bit ends at RT10 instead of RT16 but is still there for the stop bit
data samples at RT8, RT9, and RT10.
STOP
IDLE OR NEXT CHARACTER
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RECEIVER
RT CLOCK
DATA
SAMPLES
Figure 12-9. Fast Data
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 12-9, the receiver counts 154 RT cycles at the point
when the count of the transmitting device is 10 bit times × 16 RT cycles = 160 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit
character with no errors is
154 – 160 × 100 = 3.90%.
-------------------------154
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 12-9, the receiver counts 170 RT cycles at the point
when the count of the transmitting device is 11 bit times × 16 RT cycles = 176 RT cycles.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
122
Freescale Semiconductor
Functional Description
The maximum percent difference between the receiver count and the transmitter count of a fast 9-bit
character with no errors is
170 – 176 × 100 = 3.53%.
-------------------------170
12.4.3.6 Receiver Wakeup
So that the MCU can ignore transmissions intended only for other receivers in multiple-receiver systems,
the receiver can be put into a standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the
receiver into a standby state during which receiver interrupts are disabled.
Depending on the state of the WAKE bit in SCC1, either of two conditions on the RxD pin can bring the
receiver out of the standby state:
1. Address mark — An address mark is a 1 in the most significant bit position of a received character.
When the WAKE bit is set, an address mark wakes the receiver from the standby state by clearing
the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can then
compare the character containing the address mark to the user-defined address of the receiver. If
they are the same, the receiver remains awake and processes the characters that follow. If they
are not the same, software can set the RWU bit and put the receiver back into the standby state.
2. Idle input line condition — When the WAKE bit is clear, an idle character on the RxD pin wakes the
receiver from the standby state by clearing the RWU bit. The idle character that wakes the receiver
does not set the receiver idle bit, IDLE, or the SCI receiver full bit, SCRF. The idle line type bit,
ILTY, determines whether the receiver begins counting 1s as idle character bits after the start bit
or after the stop bit.
NOTE
With the WAKE bit clear, setting the RWU bit after the RxD pin has been
idle may cause the receiver to wake up immediately.
12.4.3.7 Receiver Interrupts
These sources can generate CPU interrupt requests from the SCI receiver:
• SCI receiver full (SCRF) — The SCRF bit in SCS1 indicates that the receive shift register has
transferred a character to the SCDR. SCRF can generate a receiver CPU interrupt request. Setting
the SCI receive interrupt enable bit, SCRIE, in SCC2 enables the SCRF bit to generate receiver
CPU interrupts.
• Idle input (IDLE) — The IDLE bit in SCS1 indicates that 10 or 11 consecutive 1s shifted in from the
RxD pin. The idle line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate CPU
interrupt requests.
12.4.3.8 Error Interrupts
These receiver error flags in SCS1 can generate CPU interrupt requests:
• Receiver overrun (OR) — The OR bit indicates that the receive shift register shifted in a new
character before the previous character was read from the SCDR. The previous character remains
in the SCDR, and the new character is lost. The overrun interrupt enable bit, ORIE, in SCC3
enables OR to generate SCI error CPU interrupt requests.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
123
Serial Communications Interface Module (SCI)
•
•
•
Noise flag (NF) — The NF bit is set when the SCI detects noise on incoming data or break
characters, including start, data, and stop bits. The noise error interrupt enable bit, NEIE, in SCC3
enables NF to generate SCI error CPU interrupt requests.
Framing error (FE) — The FE bit in SCS1 is set when a 0 occurs where the receiver expects a stop
bit. The framing error interrupt enable bit, FEIE, in SCC3 enables FE to generate SCI error CPU
interrupt requests.
Parity error (PE) — The PE bit in SCS1 is set when the SCI detects a parity error in incoming data.
The parity error interrupt enable bit, PEIE, in SCC3 enables PE to generate SCI error CPU interrupt
requests.
12.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes.
12.5.1 Wait Mode
The SCI module remains active in wait mode. Any enabled CPU interrupt request from the SCI module
can bring the MCU out of wait mode.
If SCI module functions are not required during wait mode, reduce power consumption by disabling the
module before executing the WAIT instruction.
12.5.2 Stop Mode
The SCI module is inactive in stop mode. The STOP instruction does not affect SCI register states. SCI
module operation resumes after the MCU exits stop mode.
Because the internal clock is inactive during stop mode, entering stop mode during an SCI transmission
or reception results in invalid data.
12.6 I/O Signals
Port B shares two of its pins with the SCI module. The two SCI I/O pins are:
• TxD — Transmit data
• RxD — Receive data
12.6.1 TxD (Transmit Data)
The TxD pin is the serial data output from the SCI transmitter. The SCI shares the TxD pin with port B.
When the SCI is enabled, the TxD pin is an output regardless of the state of the DDRB5 bit in data
direction register B (DDRB).
12.6.2 RxD (Receive Data)
The RxD pin is the serial data input to the SCI receiver. The SCI shares the RxD pin with port B. When
the SCI is enabled, the RxD pin is an input regardless of the state of the DDRB4 bit in data direction
register B (DDRB).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Freescale Semiconductor
I/O Registers
12.7 I/O Registers
These I/O registers control and monitor SCI operation:
• SCI control register 1 (SCC1)
• SCI control register 2 (SCC2)
• SCI control register 3 (SCC3)
• SCI status register 1 (SCS1)
• SCI status register 2 (SCS2)
• SCI data register (SCDR)
• SCI baud rate register (SCBR)
12.7.1 SCI Control Register 1
SCI control register 1 (SCC1):
• Enables loop mode operation
• Enables the SCI
• Controls output polarity
• Controls character length
• Controls SCI wakeup method
• Controls idle character detection
• Enables parity function
• Controls parity type
Address:
$0013
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
LOOPS
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
0
Figure 12-10. SCI Control Register 1 (SCC1)
LOOPS — Loop Mode Select Bit
This read/write bit enables loop mode operation. In loop mode the RxD pin is disconnected from the
SCI, and the transmitter output goes into the receiver input. Both the transmitter and the receiver must
be enabled to use loop mode. Reset clears the LOOPS bit.
1 = Loop mode enabled
0 = Normal operation enabled
ENSCI — Enable SCI Bit
This read/write bit enables the SCI and the SCI baud rate generator. Clearing ENSCI sets the SCTE
and TC bits in SCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit.
1 = SCI enabled
0 = SCI disabled
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
125
Serial Communications Interface Module (SCI)
TXINV — Transmit Inversion Bit
This read/write bit reverses the polarity of transmitted data. Reset clears the TXINV bit.
1 = Transmitter output inverted
0 = Transmitter output not inverted
NOTE
Setting the TXINV bit inverts all transmitted values, including idle, break,
start, and stop bits.
M — Mode (Character Length) Bit
This read/write bit determines whether SCI characters are eight or nine bits long. (See Table 12-5.)
The ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. Reset clears
the M bit.
1 = 9-bit SCI characters
0 = 8-bit SCI characters
WAKE — Wakeup Condition Bit
This read/write bit determines which condition wakes up the SCI: a 1 (address mark) in the most
significant bit position of a received character or an idle condition on the RxD pin. Reset clears the
WAKE bit.
1 = Address mark wakeup
0 = Idle line wakeup
ILTY — Idle Line Type Bit
This read/write bit determines when the SCI starts counting 1s as idle character bits. The counting
begins either after the start bit or after the stop bit. If the count begins after the start bit, then a string
of 1s preceding the stop bit may cause false recognition of an idle character. Beginning the count after
the stop bit avoids false idle character recognition, but requires properly synchronized transmissions.
Reset clears the ILTY bit.
1 = Idle character bit count begins after stop bit.
0 = Idle character bit count begins after start bit.
PEN — Parity Enable Bit
This read/write bit enables the SCI parity function. (See Table 12-5.) When enabled, the parity function
inserts a parity bit in the most significant bit position. (See Figure 12-2.) Reset clears the PEN bit.
1 = Parity function enabled
0 = Parity function disabled
PTY — Parity Bit
This read/write bit determines whether the SCI generates and checks for odd parity or even parity.
(See Table 12-5.) Reset clears the PTY bit.
1 = Odd parity
0 = Even parity
NOTE
Changing the PTY bit in the middle of a transmission or reception can
generate a parity error.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
126
Freescale Semiconductor
I/O Registers
Table 12-5. Character Format Selection
Control Bits
Character Format
M
PEN–PTY
Start
Bits
Data
Bits
Parity
Stop
Bits
Character
Length
0
0X
1
8
None
1
10 Bits
1
0X
1
9
None
1
11 Bits
0
10
1
7
Even
1
10 Bits
0
11
1
7
Odd
1
10 Bits
1
10
1
8
Even
1
11 Bits
1
11
1
8
Odd
1
11 Bits
12.7.2 SCI Control Register 2
SCI control register 2 (SCC2):
• Enables these CPU interrupt requests:
– Enables the SCTE bit to generate transmitter CPU interrupt requests
– Enables the TC bit to generate transmitter CPU interrupt requests
– Enables the SCRF bit to generate receiver CPU interrupt requests
– Enables the IDLE bit to generate receiver CPU interrupt requests
• Enables the transmitter
• Enables the receiver
• Enables SCI wakeup
• Transmits SCI break characters
Address:
$0014
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
Figure 12-11. SCI Control Register 2 (SCC2)
SCTIE — SCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate SCI transmitter CPU interrupt requests. Setting
the SCTIE bit in SCC3 enables the SCTE bit to generate CPU interrupt requests. Reset clears the
SCTIE bit.
1 = SCTE enabled to generate CPU interrupt
0 = SCTE not enabled to generate CPU interrupt
TCIE — Transmission Complete Interrupt Enable Bit
This read/write bit enables the TC bit to generate SCI transmitter CPU interrupt requests. Reset clears
the TCIE bit.
1 = TC enabled to generate CPU interrupt requests
0 = TC not enabled to generate CPU interrupt requests
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
127
Serial Communications Interface Module (SCI)
SCRIE — SCI Receive Interrupt Enable Bit
This read/write bit enables the SCRF bit to generate SCI receiver CPU interrupt requests. Setting the
SCRIE bit in SCC3 enables the SCRF bit to generate CPU interrupt requests. Reset clears the SCRIE
bit.
1 = SCRF enabled to generate CPU interrupt
0 = SCRF not enabled to generate CPU interrupt
ILIE — Idle Line Interrupt Enable Bit
This read/write bit enables the IDLE bit to generate SCI receiver CPU interrupt requests. Reset clears
the ILIE bit.
1 = IDLE enabled to generate CPU interrupt requests
0 = IDLE not enabled to generate CPU interrupt requests
TE — Transmitter Enable Bit
Setting this read/write bit begins the transmission by sending a preamble of 10 or 11 1s from the
transmit shift register to the TxD pin. If software clears the TE bit, the transmitter completes any
transmission in progress before the TxD returns to the idle condition (logic 1). Clearing and then setting
TE during a transmission queues an idle character to be sent after the character currently being
transmitted. Reset clears the TE bit.
1 = Transmitter enabled
0 = Transmitter disabled
NOTE
Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is clear.
ENSCI is in SCI control register 1.
RE — Receiver Enable Bit
Setting this read/write bit enables the receiver. Clearing the RE bit disables the receiver but does not
affect receiver interrupt flag bits. Reset clears the RE bit.
1 = Receiver enabled
0 = Receiver disabled
NOTE
Writing to the RE bit is not allowed when the enable SCI bit (ENSCI) is
clear. ENSCI is in SCI control register 1.
RWU — Receiver Wakeup Bit
This read/write bit puts the receiver in a standby state during which receiver interrupts are disabled.
The WAKE bit in SCC1 determines whether an idle input or an address mark brings the receiver out
of the standby state and clears the RWU bit. Reset clears the RWU bit.
1 = Standby state
0 = Normal operation
SBK — Send Break Bit
Setting and then clearing this read/write bit transmits a break character followed by a 1. The 1 after the
break character guarantees recognition of a valid start bit. If SBK remains set, the transmitter
continuously transmits break characters with no 1s between them. Reset clears the SBK bit.
1 = Transmit break characters
0 = No break characters being transmitted
NOTE
Do not toggle the SBK bit immediately after setting the SCTE bit. Toggling
SBK before the preamble begins causes the SCI to send a break character
instead of a preamble.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
128
Freescale Semiconductor
I/O Registers
12.7.3 SCI Control Register 3
SCI control register 3 (SCC3):
• Stores the ninth SCI data bit received and the ninth SCI data bit to be transmitted.
• Enables these interrupts:
– Receiver overrun interrupts
– Noise error interrupts
– Framing error interrupts
– Parity error interrupts
Address:
$0015
Bit 7
Read:
R8
Write:
Reset:
U
6
5
4
3
2
1
Bit 0
T8
R
R
ORIE
NEIE
FEIE
PEIE
U
0
0
0
0
0
0
R
= Reserved
= Unimplemented
U = Unaffected
Figure 12-12. SCI Control Register 3 (SCC3)
R8 — Received Bit 8
When the SCI is receiving 9-bit characters, R8 is the read-only ninth bit (bit 8) of the received character.
R8 is received at the same time that the SCDR receives the other eight bits.
When the SCI is receiving 8-bit characters, R8 is a copy of the eighth bit (bit 7). Reset has no effect on
the R8 bit.
T8 — Transmitted Bit 8
When the SCI is transmitting 9-bit characters, T8 is the read/write ninth bit (bit 8) of the transmitted
character. T8 is loaded into the transmit shift register at the same time that the SCDR is loaded into
the transmit shift register. Reset has no effect on the T8 bit.
ORIE — Receiver Overrun Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the receiver overrun bit, OR.
1 = SCI error CPU interrupt requests from OR bit enabled
0 = SCI error CPU interrupt requests from OR bit disabled
NEIE — Receiver Noise Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the noise error bit, NE.
Reset clears NEIE.
1 = SCI error CPU interrupt requests from NE bit enabled
0 = SCI error CPU interrupt requests from NE bit disabled
FEIE — Receiver Framing Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the framing error bit, FE.
Reset clears FEIE.
1 = SCI error CPU interrupt requests from FE bit enabled
0 = SCI error CPU interrupt requests from FE bit disabled
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Serial Communications Interface Module (SCI)
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables SCI receiver CPU interrupt requests generated by the parity error bit, PE.
Reset clears PEIE.
1 = SCI error CPU interrupt requests from PE bit enabled
0 = SCI error CPU interrupt requests from PE bit disabled
NOTE
Bits 5 and 4 are reserved for MCUs with a direct-memory access (DMA)
module. Because the MC68HC908KX8 does not have a DMA module,
these bits should not be set.
12.7.4 SCI Status Register 1
SCI status register 1 (SCS1) contains flags to signal these conditions:
• Transfer of SCDR data to transmit shift register complete
• Transmission complete
• Transfer of receive shift register data to SCDR complete
• Receiver input idle
• Receiver overrun
• Noisy data
• Framing error
• Parity error
Address:
$0016
Bit 7
6
5
4
3
2
1
Bit 0
Read:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 12-13. SCI Status Register 1 (SCS1)
SCTE — SCI Transmitter Empty Bit
This clearable, read-only bit is set when the SCDR transfers a character to the transmit shift register.
SCTE can generate an SCI transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set,
SCTE generates an SCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit by
reading SCS1 with SCTE set and then writing to SCDR. Reset sets the SCTE bit.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
TC — Transmission Complete Bit
This read-only bit is set when the SCTE bit is set, and no data, preamble, or break character is being
transmitted. TC generates an SCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also set.
TC is cleared automatically when data, preamble, or break is queued and ready to be sent. There may
be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the
transmission actually starting. Reset sets the TC bit.
1 = No transmission in progress
0 = Transmission in progress
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I/O Registers
SCRF — SCI Receiver Full Bit
This clearable, read-only bit is set when the data in the receive shift register transfers to the SCI data
register. SCRF can generate an SCI receiver CPU interrupt request. When the SCRIE bit in SCC2 is
set the SCRF generates a CPU interrupt request. In normal operation, clear the SCRF bit by reading
SCS1 with SCRF set and then reading the SCDR. Reset clears SCRF.
1 = Received data available in SCDR
0 = Data not available in SCDR
IDLE — Receiver Idle Bit
This clearable, read-only bit is set when 10 or 11 consecutive 1s appear on the receiver input. IDLE
generates an SCI error CPU interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE bit by
reading SCS1 with IDLE set and then reading the SCDR. After the receiver is enabled, it must receive
a valid character that sets the SCRF bit before an idle condition can set the IDLE bit. Also, after the
IDLE bit has been cleared, a valid character must again set the SCRF bit before an idle condition can
set the IDLE bit. Reset clears the IDLE bit.
1 = Receiver input idle
0 = Receiver input active (or idle since the IDLE bit was cleared)
OR — Receiver Overrun Bit
This clearable, read-only bit is set when software fails to read the SCDR before the receive shift
register receives the next character. The OR bit generates an SCI error CPU interrupt request if the
ORIE bit in SCC3 is also set. The data in the shift register is lost, but the data already in the SCDR is
not affected. Clear the OR bit by reading SCS1 with OR set and then reading the SCDR. Reset clears
the OR bit.
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
Software latency may allow an overrun to occur between reads of SCS1 and SCDR in the flag-clearing
sequence. Figure 12-14 shows the normal flag-clearing sequence and an example of an overrun
caused by a delayed flag-clearing sequence. The delayed read of SCDR does not clear the OR bit
because OR was not set when SCS1 was read. Byte 2 caused the overrun and is lost. The next
flag-clearing sequence reads byte 3 in the SCDR instead of byte 2.
In applications that are subject to software latency or in which it is important to know which byte is lost
due to an overrun, the flag-clearing routine can check the OR bit in a second read of SCS1 after
reading the data register.
NF — Receiver Noise Flag Bit
This clearable, read-only bit is set when the SCI detects noise on the RxD pin. NF generates an NF
CPU interrupt request if the NEIE bit in SCC3 is also set. Clear the NF bit by reading SCS1 and then
reading the SCDR. Reset clears the NF bit.
1 = Noise detected
0 = No noise detected
FE — Receiver Framing Error Bit
This clearable, read-only bit is set when a 0 is accepted as the stop bit. FE generates an SCI error CPU
interrupt request if the FEIE bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set and
then reading the SCDR. Reset clears the FE bit.
1 = Framing error detected
0 = No framing error detected
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Serial Communications Interface Module (SCI)
BYTE 1
BYTE 2
BYTE 3
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
NORMAL FLAG CLEARING SEQUENCE
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCDR
BYTE 1
READ SCDR
BYTE 2
READ SCDR
BYTE 3
BYTE 1
BYTE 2
SCRF = 0
OR = 0
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 1
SCRF = 1
OR = 1
DELAYED FLAG CLEARING SEQUENCE
BYTE 3
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 1
READ SCDR
BYTE 3
Figure 12-14. Flag Clearing Sequence
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the SCI detects a parity error in incoming data. PE generates
a PE CPU interrupt request if the PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with
PE set and then reading the SCDR. Reset clears the PE bit.
1 = Parity error detected
0 = No parity error detected
12.7.5 SCI Status Register 2
SCI status register 2 (SCS2) contains flags to signal these conditions:
• Break character detected
• Incoming data
Address:
Read:
$0017
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
BKF
RPF
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 12-15. SCI Status Register 2 (SCS2)
BKF — Break Flag Bit
This clearable, read-only bit is set when the SCI detects a break character on the RxD pin. In SCS1,
the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in SCC3 is cleared. BKF
does not generate a CPU interrupt request. Clear BKF by reading SCS2 with BKF set and then reading
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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I/O Registers
the SCDR. Once cleared, BKF can become set again only after 1s again appear on the RxD pin
followed by another break character. Reset clears the BKF bit.
1 = Break character detected
0 = No break character detected
RPF — Reception-in-Progress Flag Bit
This read-only bit is set when the receiver detects a 0 during the RT1 time period of the start bit search.
RPF does not generate an interrupt request. RPF is reset after the receiver detects false start bits
(usually from noise or a baud rate mismatch), or when the receiver detects an idle character. Polling
RPF before disabling the SCI module or entering stop mode can show whether a reception is in
progress.
1 = Reception in progress
0 = No reception in progress
12.7.6 SCI Data Register
The SCI data register (SCDR) is the buffer between the internal data bus and the receive and transmit
shift registers. Reset has no effect on data in the SCI data register.
Address:
$0018
Bit 7
6
5
4
3
2
1
Bit 0
Read:
R7
R6
R5
R4
R3
R2
R1
R0
Write:
T7
T6
T5
T4
T3
T2
T1
T0
Reset:
Unaffected by reset
Figure 12-16. SCI Data Register (SCDR)
R7/T7–R0/T0 — Receive/Transmit Data Bits
Reading address $0018 accesses the read-only received data bits, R7–R0. Writing to address $0018
writes the data to be transmitted, T7–T0. Reset has no effect on the SCI data register.
NOTE
Do not use read-modify-write instructions on the SCI data register.
12.7.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter.
Address:
$0019
Read:
Bit 7
6
0
0
0
0
Write:
Reset:
5
4
3
2
1
Bit 0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
R
= Reserved
= Unimplemented
Figure 12-17. SCI Baud Rate Register (SCBR)
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Serial Communications Interface Module (SCI)
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown in Table 12-6. Reset clears SCP1
and SCP0.
Table 12-6. SCI Baud Rate Prescaling
SCP[1:0]
Prescaler Divisor (PD)
00
1
01
3
10
4
11
13
SCR2–SCR0 — SCI Baud Rate Select Bits
These read/write bits select the SCI baud rate divisor as shown in Table 12-7. Reset clears
SCR2–SCR0.
Table 12-7. SCI Baud Rate Selection
SCR[2:1:0]
Baud Rate Divisor (BD)
000
1
001
2
010
4
011
8
100
16
101
32
110
64
111
128
Use this formula to calculate the SCI baud rate:
f BAUDCLK
Baud rate = -----------------------------------64 × PD × BD
where:
fBAUDCLK = baud clock frequency
PD = prescaler divisor
BD = baud rate divisor
Table 12-8 shows the SCI baud rates that can be generated with a 4.9152-MHz CGMXCLK frequency.
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I/O Registers
Table 12-8. SCI Baud Rate Selection Examples
SCP[1:0]
Prescaler
Divisor
(PD)
SCR[2:1:0]
Baud Rate
Divisor
(BD)
Baud Rate
(fBAUDCLK = 4.9152 MHz)
00
1
000
1
76,800
00
1
001
2
38,400
00
1
010
4
19,200
00
1
011
8
9600
00
1
100
16
4800
00
1
101
32
2400
00
1
110
64
1200
00
1
111
128
600
01
3
000
1
25,600
01
3
001
2
12,800
01
3
010
4
6400
01
3
011
8
3200
01
3
100
16
1600
01
3
101
32
800
01
3
110
64
400
01
3
111
128
200
10
4
000
1
19,200
10
4
001
2
9600
10
4
010
4
4800
10
4
011
8
2400
10
4
100
16
1200
10
4
101
32
600
10
4
110
64
300
10
4
111
128
150
11
13
000
1
5908
11
13
001
2
2954
11
13
010
4
1477
11
13
011
8
739
11
13
100
16
369
11
13
101
32
185
11
13
110
64
92
11
13
111
128
46
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Serial Communications Interface Module (SCI)
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Freescale Semiconductor
Chapter 13
System Integration Module (SIM)
13.1 Introduction
This section describes the system integration module (SIM), which supports up to 24 external and/or
internal interrupts. The SIM is a system state controller that coordinates the central processor unit (CPU)
and exception timing. Together with the CPU, the SIM controls all microcontroller unit (MCU) activities.
Figure 13-1 is a summary of the SIM input/output (I/O) registers. A block diagram of the SIM is shown in
Figure 13-2.
The SIM is responsible for:
• Bus clock generation and control for CPU and peripherals:
– Stop/wait/reset entry and recovery
– Internal clock control
• Master reset control, including power-on reset (POR) and computer operating properly (COP)
timeout
• Interrupt control:
– Acknowledge timing
– Arbitration control timing
– Vector address generation
• CPU enable/disable timing
• Modular architecture expandable to 128 interrupt sources
Addr.
Bit 7
6
5
4
3
2
1
Bit 0
SIM Reset Status Register Read:
(SRSR) Write:
See page 148. POR:
POR
0
COP
ILOP
ILAD
MENRST
LVI
0
1
0
0
0
0
0
0
0
IF6
IF5
IF4
IF3
IF2
IF1
0
0
$FE04
Interrupt Status Register 1 Read:
(INT1) Write:
See page 149. Reset:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
$FE05
Interrupt Status Register 2 Read:
(INT2) Write:
See page 150. Reset:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Interrupt Status Register 3 Read:
(INT3) Write:
See page 150. Reset:
IF22
IF21
IF20
IF19
IF18
IF17
IF16
IF15
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
= Reserved
$FE01
$FE06
Register Name
= Unimplemented
Figure 13-1. SIM I/O Register Summary
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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System Integration Module (SIM)
MODULE STOP
MODULE WAIT
CPU STOP (FROM CPU)
CPU WAIT (FROM CPU)
STOP/WAIT
CONTROL
SIMOSCEN (TO ICG)
SIM
COUNTER
COP CLOCK
CGMXCLK (FROM ICG)
CGMOUT (FROM ICG)
÷2
CLOCK
CONTROL
INTERNAL CLOCKS
CLOCK GENERATORS
FORCED MON MODE ENTRY
(FROM MENRST MODULE)
POR CONTROL
MASTER
RESET
CONTROL
SIM RESET STATUS REGISTER
LVI (FROM LVI MODULE)
ILLEGAL OPCODE (FROM CPU)
ILLEGAL ADDRESS (FROM ADDRESS
MAP DECODERS)
COP (FROM COP MODULE)
RESET
INTERRUPT CONTROL
AND PRIORITY DECODE
INTERRUPT SOURCES
CPU INTERFACE
Figure 13-2. SIM Block Diagram
Table 13-1 shows the internal signal names used in this section.
Table 13-1. Signal Name Conventions
Signal Name
Description
CGMXCLK
Selected clock source from internal clock generator module (ICG)
CGMOUT
Clock output from ICG module (bus clock = CGMOUT divided by two)
IAB
Internal address bus
IDB
Internal data bus
PORRST
Signal from the power-on reset (POR) module to the SIM
IRST
Internal reset signal
R/W
Read/write signal
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SIM Bus Clock Control and Generation
13.2 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and peripherals on the MCU. The
system clocks are generated from an incoming clock, CGMOUT, as shown in Figure 13-3. This clock
originates from either an external oscillator or from the internal clock generator.
CGMXCLK
ECLK
CLOCK
SELECT
CIRCUIT
÷2
ICLK
ICG
GENERATOR
A
CGMOUT
B S*
*WHEN S = 1,
CGMOUT = B
SIM COUNTER
÷2
BUS CLOCK
GENERATORS
SIM
CS
MONITOR MODE
USER MODE
ICG
Figure 13-3. System Clock Signals
13.2.1 Bus Timing
In user mode, the internal bus frequency is the internal clock generator output (CGMXCLK) divided by
four.
13.2.2 Clock Startup from POR or LVI Reset
When the power-on reset (POR) module or the low-voltage inhibit (LVI) module generates a reset, the
clocks to the CPU and peripherals are inactive and held in an inactive phase until after 4096 CGMXCLK
cycles. The MCU is held in reset by the SIM during this entire period. The bus clocks start upon completion
of the timeout.
13.2.3 Clocks in Stop Mode and Wait Mode
Upon exit from stop mode by an interrupt or reset, the SIM allows CGMXCLK to clock the SIM counter.
The CPU and peripheral clocks do not become active until after the stop delay timeout. Stop mode
recovery timing is discussed in detail in 13.6.2 Stop Mode.
In wait mode, the CPU clocks are inactive. Refer to the wait mode subsection of each module to see if the
module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode.
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System Integration Module (SIM)
13.3 Reset and System Initialization
The MCU has these internal reset sources:
• Power-on reset (POR) module
• Computer operating properly (COP) module
• Low-voltage inhibit (LVI) module
• Illegal opcode
• Illegal address
• Forced monitor mode entry reset (MENRST) module
All of these resets produce the vector $FFFE–$FFFF ($FEFE–$FEFF in monitor mode) and assert the
internal reset signal (IRST). IRST causes all registers to be returned to their default values and all
modules to be returned to their reset states.
These internal resets clear the SIM counter and set a corresponding bit in the SIM reset status register
(SRSR). See 13.4 SIM Counter and 13.7.1 SIM Reset Status Register.
13.3.1 Active Resets from Internal Sources
An internal reset can be caused by an illegal address, illegal opcode, COP timeout, LVI, POR, or
MENRST as shown in Figure 13-4.
NOTE
For LVI or POR resets, the SIM cycles through 4096 CGMXCLK cycles
during which the SIM asserts IRST. The internal reset signal then follows
with the 64-cycle phase as shown in Figure 13-5.
The COP reset is asynchronous to the bus clock.
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
POR
MENRST
INTERNAL RESET
Figure 13-4. Sources of Internal Reset
IRST
64 CYCLES
CGMXCLK
IAB
VECTOR HIGH
Figure 13-5. Internal Reset Timing
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Reset and System Initialization
13.3.1.1 Power-On Reset
When power is first applied to the MCU, the power-on reset (POR) module generates a pulse to indicate
that power-on has occurred. The MCU is held in reset while the SIM counter counts out 4096 CGMXCLK
cycles. Another 64 CGMXCLK cycles later, the CPU and memories are released from reset to allow the
reset vector sequence to occur.
At power-on, these events occur:
• A POR pulse is generated.
• The internal reset signal is asserted.
• The SIM enables CGMOUT.
• Internal clocks to the CPU and modules are held inactive for 4096 CGMXCLK cycles to allow
stabilization of the internal clock generator.
• The POR bit of the SIM reset status register (SRSR) is set and all other bits in the register are
cleared.
PORRST
4096
CYCLES
64
CYCLES
CGMXCLK
CGMOUT
IRST
IAB
$FFFE
$FFFF
Figure 13-6. POR Recovery
13.3.1.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of the COP counter causes an
internal reset and sets the COP bit in the reset status register (SRSR).
To prevent a COP module timeout, write any value to location $FFFF. Writing to location $FFFF clears
the COP counter and stages 12–5 of the SIM counter. The SIM counter output, which occurs at least
every 212–24 CGMXCLK cycles, drives the COP counter. The COP should be serviced as soon as
possible out of reset to guarantee the maximum amount of time before the first timeout.
The COP module is disabled if the IRQ1 pin is held at VTST while the MCU is in monitor mode. The COP
module can be disabled only through combinational logic conditioned with the high-voltage signal on the
IRQ1 pin. This prevents the COP from becoming disabled as a result of external noise.
13.3.1.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP
bit in the SIM reset status register (SRSR) and causes a reset.
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System Integration Module (SIM)
If the stop enable bit, STOP, in the configuration register (CONFIG1) is 0, the SIM treats the STOP
instruction as an illegal opcode and causes an illegal opcode reset.
13.3.1.4 Illegal Address Reset
An opcode fetch from an unmapped address generates an illegal address reset. The SIM verifies that the
CPU is fetching an opcode prior to asserting the ILAD bit in the SIM reset status register (SRSR) and
resetting the MCU. A data fetch from an unmapped address does not generate a reset.
13.3.1.5 Forced Monitor Mode Entry Reset (MENRST)
The MENRST module is monitoring the reset vector fetches and will assert an internal reset if it detects
that the reset vectors are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode.
See 16.3 Monitor ROM (MON).
13.3.1.6 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when the VDD voltage falls to the VTRIPF
voltage. The LVI bit in the SIM reset status register (SRSR) is set and a chip reset is asserted if the
LVIPWRD and LVIRSTD bits in the CONFIG register are at 0. The MCU is held in reset until VDD rises
above VTRIPR. The MCU remains in reset until the SIM counts 4096 CGMXCLK to begin a reset recovery.
Another 64 CGMXCLK cycles later, the CPU is released from reset to allow the reset vector sequence to
occur. See Chapter 10 Low-Voltage Inhibit (LVI).
13.4 SIM Counter
The SIM counter is used by the power-on reset module (POR) and in stop mode recovery to allow the
oscillator time to stabilize before enabling the internal bus (IBUS) clocks. The SIM counter also serves as
a prescaler for the computer operating properly module (COP). The SIM counter overflow supplies the
clock for the COP module. The SIM counter is 12 bits long and is clocked by the falling edge of
CGMXCLK.
13.4.1 SIM Counter During Power-On Reset
The power-on reset module (POR) detects power applied to the MCU. At power-on, the POR circuit
asserts the signal PORRST. Once the SIM is initialized, it enables the internal clock generator to drive the
bus clock state machine.
13.4.2 SIM Counter During Stop Mode Recovery
The SIM counter also is used for stop mode recovery. The STOP instruction clears the SIM counter. After
an interrupt or reset, the SIM senses the state of the short stop recovery bit, SSREC, in the configuration
register. If the SSREC bit is a 1, then the stop recovery is reduced from the normal delay of 4096
CGMXCLK cycles down to 32 CGMXCLK cycles.
13.4.3 SIM Counter and Reset States
The SIM counter is free-running after all reset states. See 13.3.1 Active Resets from Internal Sources for
counter control and internal reset recovery sequences.
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Program Exception Control
13.5 Program Exception Control
Normal, sequential program execution can be changed in two ways:
1. Interrupts
a. Maskable hardware CPU interrupts
b. Non-maskable software interrupt instruction (SWI)
2. Reset
13.5.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register contents on the stack and sets the
interrupt mask (I bit) to prevent additional interrupts. At the end of an interrupt, the return-from-interrupt
(RTI) instruction recovers the CPU register contents from the stack so that normal processing can
resume. Figure 13-7 shows interrupt entry timing. Figure 13-8 shows interrupt recovery timing.
MODULE
INTERRUPT
I BIT
IAB
IDB
DUMMY
SP
DUMMY
SP – 1
SP – 2
PC – 1[7:0] PC – 1[15:8]
SP – 3
X
SP – 4
A
VECT H
CCR
VECT L START ADDR
V DATA H
V DATA L
OPCODE
R/W
Figure 13-7. Interrupt Entry
MODULE
INTERRUPT
I BIT
IAB
SP – 4
IDB
SP – 3
CCR
SP – 2
A
SP – 1
X
SP
PC
PC + 1
PC – 1 [7:0] PC – 1 [15:8] OPCODE
OPERAND
R/W
Figure 13-8. Interrupt Recovery
Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The
arbitration result is a constant that the CPU uses to determine which vector to fetch. As shown in Figure
13-9, once an interrupt is latched by the SIM, no other interrupt can take precedence, regardless of
priority, until the latched interrupt is serviced or the I bit is cleared.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
143
System Integration Module (SIM)
FROM RESET
YES
BITSET?
SET?
IIBIT
NO
IRQ1
INTERRUPT
?
NO
ICG CLK MON
INTERRUPT
?
NO
OTHER
INTERRUPTS
?
NO
YES
YES
YES
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION
?
YES
NO
RTI
INSTRUCTION
?
YES
UNSTACK CPU REGISTERS
NO
EXECUTE INSTRUCTION
Figure 13-9. Interrupt Processing
13.5.1.1 Hardware Interrupts
A hardware interrupt does not stop the current instruction. Processing of a hardware interrupt begins after
completion of the current instruction. When the current instruction is complete, the SIM checks all pending
hardware interrupts. If interrupts are not masked (I bit clear in the condition code register), and if the
corresponding interrupt enable bit is set, the SIM proceeds with interrupt processing; otherwise, the next
instruction is fetched and executed.
If more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is
serviced first. Figure 13-10 demonstrates what happens when two interrupts are pending. If an interrupt
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
144
Freescale Semiconductor
Low-Power Modes
is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the
load-accumulator- from-memory (LDA) instruction is executed.
The LDA opcode is prefetched by both the INT1 and INT2 RTI instructions. However, in the case of the
INT1 RTI prefetch, this is a redundant operation.
NOTE
To maintain compatibility with the M68HC05, M6805, and M146805
Families the H register is not pushed on the stack during interrupt entry. If
the interrupt service routine modifies the H register or uses the indexed
addressing mode, software should save the H register and then restore it
prior to exiting the routine.
CLI
BACKGROUND
ROUTINE
LDA #$FF
INT1
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 13-10. Interrupt Recognition Example
13.5.1.2 SWI Instruction
The SWI instruction is a non-maskable instruction that causes an interrupt regardless of the state of the
interrupt mask (I bit) in the condition code register.
NOTE
A software interrupt pushes PC onto the stack. A software interrupt does
not push PC – 1, as a hardware interrupt does.
13.5.2 Reset
All reset sources always have higher priority than interrupts and cannot be arbitrated.
13.6 Low-Power Modes
Executing the WAIT or STOP instruction puts the MCU in a low power- consumption mode for standby
situations. The SIM holds the CPU in a non-clocked state. Both STOP and WAIT clear the interrupt mask
(I) in the condition code register, allowing interrupts to occur. Low-power modes are exited via an interrupt
or reset.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
145
System Integration Module (SIM)
13.6.1 Wait Mode
In wait mode, the CPU clocks are inactive while one set of peripheral clocks continues to run. Figure 13-11
shows the timing for wait mode entry.
IAB
WAIT ADDR + 1
WAIT ADDR
IDB
PREVIOUS DATA
SAME
SAME
NEXT OPCODE
SAME
SAME
R/W
Note: Previous data can be operand data or the WAIT opcode, depending on the last instruction.
Figure 13-11. Wait Mode Entry Timing
A module that is active during wait mode can wake up the CPU with an interrupt if the interrupt is enabled.
Stacking for the interrupt begins one cycle after the WAIT instruction during which the interrupt occurred.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
Wait mode can also be exited by a reset. If the COP disable bit, COPD, in the configuration register is a 0,
then the computer operating properly module (COP) is enabled and remains active in wait mode.
Figure 13-12 and Figure 13-13 show the timing for WAIT recovery.
IAB
$DE0B
IDB
$A6
$A6
$DE0C
$A6
$01
$00FF
$0B
$00FE
$00FD
$00FC
$DE
EXITSTOPWAIT
Note: EXITSTOPWAIT = CPU interrupt
Figure 13-12. Wait Recovery from Interrupt
64
CYCLES
$DE0B
IAB
IDB
$A6
$A6
RST VCT H RST VCT L
$A6
IRST
CGMXCLK
Figure 13-13. Wait Recovery from Internal Reset
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
146
Freescale Semiconductor
Low-Power Modes
13.6.2 Stop Mode
In stop mode, the SIM counter is held in reset and the CPU and peripheral clocks are held inactive. If the
OSCENINSTOP bit in the configuration register is not enabled, the SIM also disables the internal clock
generator module outputs (CGMOUT and CGMXCLK).
The CPU and peripheral clocks do not become active until after the stop delay timeout. Stop mode is
exited via an interrupt request from a module that is still active in stop mode or from a system reset.
An interrupt request from a module that is still active in stop mode can cause an exit from stop mode. Stop
recovery time is selectable using the SSREC bit in the configuration register. If SSREC is set, stop
recovery is reduced from the normal delay of 4096 CGMXCLK cycles down to 32. Stacking for interrupts
begins after the selected stop recovery time has elapsed.
When stop mode is exited due to a reset condition, the SIM forces a long stop recovery time of 4096
CGMXCLK cycles.
NOTE
Short stop recovery is ideal for applications using canned oscillators that do
not require long startup times for stop mode. External crystal applications
should use the full stop recovery time by clearing the SSREC bit.
The SIM counter is held in reset from the execution of the STOP instruction until the beginning of stop
recovery. It is then used to time the recovery period. Figure 13-14 shows stop mode entry timing.
CPUSTOP
IAB
IDB
STOP ADDR
STOP ADDR + 1
PREVIOUS DATA
SAME
SAME
NEXT OPCODE
SAME
SAME
R/W
Note: Previous data can be operand data or the STOP opcode, depending on the last instruction.
Figure 13-14. Stop Mode Entry Timing
STOP RECOVERY PERIOD
CGMXCLK
INT
IAB
STOP +1
STOP + 2
STOP + 2
SP
SP – 1
SP – 2
SP – 3
Figure 13-15. Stop Mode Recovery from Interrupt
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
147
System Integration Module (SIM)
13.7 SIM Registers
The SIM has four memory mapped registers described here.
1. SIM reset status register (SRSR)
2. Interrupt status register 1 (INT1)
3. Interrupt status register 2 (INT2)
4. Interrupt status register 2 (INT3)
13.7.1 SIM Reset Status Register
This register contains five bits that show the source of the last reset. The status register will clear
automatically after reading it. A power-on reset sets the POR bit and clears all other bits in the register.
Address:
Read:
$FE01
Bit 7
6
5
4
3
2
1
Bit 0
POR
0
COP
ILOP
ILAD
MENRST
LVI
0
1
0
0
0
0
0
0
0
Write:
POR:
= Unimplemented
Figure 13-16. SIM Reset Status Register (SRSR)
POR — Power-On Reset Bit
1 = Last reset caused by POR circuit
0 = Read of SRSR
COP — Computer Operating Properly Reset Bit
1 = Last reset caused by COP counter
0 = POR or read of SRSR
ILOP — Illegal Opcode Reset Bit
1 = Last reset caused by an illegal opcode
0 = POR or read of SRSR
ILAD — Illegal Address Reset Bit (opcode fetches only)
1 = Last reset caused by an opcode fetch from an illegal address
0 = POR or read of SRSR
MENRST — Forced Monitor Mode Entry Reset Bit
1 = Last reset was caused by the MENRST circuit
0 = POR or read of SRSR
LVI — Low-Voltage Inhibit Reset Bit
1 = Last reset was caused by the LVI circuit
0 = POR or read of SRSR
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
148
Freescale Semiconductor
SIM Registers
13.7.2 Interrupt Status Registers
The flags in the interrupt status registers identify maskable interrupt sources. The interrupt sources and
the interrupt status register flags that they set are summarized in Table 13-2. The interrupt status registers
can be useful for debugging.
Table 13-2. Interrupt Sources
Source
SWI instruction
IRQ1 pin
Flag
Mask(1)
INT
Register
Flag
Priority(2)
Vector
Address
—
—
—
0
$FFFC–$FFFD
IRQF1
IMASK1
IF1
1
$FFFA–$FFFB
ICG clock monitor
CMF
CMIE
IF2
2
$FFF8–$FFF9
TIM channel 0
CH0F
CH0IE
IF3
3
$FFF6–$FFF7
TIM channel 1
CH1F
CH1IE
IF4
4
$FFF4–$FFF5
IF5
5
$FFF2–$FFF3
IF11
6
$FFE6–$FFE7
IF12
7
$FFE4–$FFE5
IF13
8
$FFE2–$FFE3
TIM overflow
TOF
TOIE
SCI receiver overrun error
OR
ORIE
SCI receiver noise error
NF
NEIE
SCI receiver framing error
FE
FEIE
SCI receiver parity error
PE
PEIE
SCI receiver full
SCRF
SCRIE
SCI receiver idle
IDLE
ILIE
SCI transmitter empty
SCTE
SCTIE
TC
TCIE
KEYF
IMASKK
IF14
9
$FFE0–$FFE1
—
AIEN
IF15
10
$FFDE–$FFDF
TBIE
TBF
IF16
11
$FFDC–$FFDD
SCI transmission complete
Keyboard pins
ADC conversion complete
Timebase module
1. The I bit in the condition code register is a global mask for all interrupt sources except the SWI
instruction.
2. 0 = highest priority
13.7.2.1 Interrupt Status Register 1
Address:
$FE04
Bit 7
6
5
4
3
2
1
Bit 0
Read:
IF6
IF5
IF4
IF3
IF2
IF1
0
0
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 13-17. Interrupt Status Register 1 (INT1)
IF5–IF1 — Interrupt Flags 5, 4, 3, 2, and 1
These flags indicate the presence of interrupt requests from the sources shown in Table 13-2.
1 = Interrupt request present
0 = No interrupt request present
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
149
System Integration Module (SIM)
IF6 — Interrupt Flag 6
Since the MC68HC908KX8 parts do not use this interrupt flag, this bit will always read 0.
Bit 0 and Bit 1 — Always read 0
13.7.2.2 Interrupt Status Register 2
Address:
$FE05
Bit 7
6
5
4
3
2
1
Bit 0
Read:
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 13-18. Interrupt Status Register 2 (INT2)
IF14–IF11 — Interrupt Flags 14–11
These flags indicate the presence of interrupt requests from the sources shown in Table 13-2.
1 = Interrupt request present
0 = No interrupt request present
IF10–IF7 — Interrupt Flags 10–7
Since the MC68HC908KX8 parts do not use these interrupt flags, these bits will always read 0.
13.7.2.3 Interrupt Status Register 3
Address:
$FE06
Bit 7
6
5
4
3
2
1
Bit 0
Read:
IF22
IF21
IF20
IF19
IF18
IF17
IF16
IF15
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 13-19. Interrupt Status Register 3 (INT3)
IF22–IF17 — Interrupt Flags 22–17
Since the MC68HC908KX8 parts do not use these interrupt flags, these bits will always read 0.
IF16–IF15 — Interrupt Flags 16–15
These flags indicate the presence of interrupt requests from the sources shown in Table 13-2.
1 = Interrupt request present
0 = No interrupt request present
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
150
Freescale Semiconductor
Chapter 14
Timebase Module (TBM)
14.1 Introduction
This section describes the timebase module (TBM). The TBM will generate periodic interrupts at user
selectable rates using a counter clocked by either the internal or external clock sources. This TBM version
uses 15 divider stages, eight of which are user selectable.
14.2 Features
Features of the TBM module include:
• Software configurable periodic interrupts with divide by 8, 16, 32, 64, 128, 2048, 8192, and 32,768
taps of the selected clock source
• Configurable for operation during stop mode to allow periodic wake up from stop
14.3 Functional Description
This module can generate a periodic interrupt by dividing the clock source supplied from the internal clock
generator module, TBMCLK. Note that this clock source is the external clock ECLK when the ECGON bit
in the ICG control register (ICGCR) is set. Otherwise, TBMCLK is driven at the internally generated clock
frequency (ICLK). In other words, if the external clock is enabled it will be used as the TBMCLK, even if
the MCU bus clock is based on the internal clock.
The counter is initialized to all 0s when TBON bit is cleared. The counter, shown in Figure 14-1, starts
counting when the TBON bit is set. When the counter overflows at the tap selected by TBR2–TBR0, the
TBIF bit gets set. If the TBIE bit is set, an interrupt request is sent to the CPU. The TBIF flag is cleared
by writing a 1 to the TACK bit. The first time the TBIF flag is set after enabling the timebase module, the
interrupt is generated at approximately half of the overflow period. Subsequent events occur at the exact
period.
The timebase module may remain active after execution of the STOP instruction if the internal clock
generator has been enabled to operate during stop mode through the OSCENINSTOP bit in the
configuration register. The timebase module can be used in this mode to generate a periodic wakeup from
stop mode.
14.4 Interrupts
The timebase module can periodically interrupt the CPU with a rate defined by the selected TBMCLK and
the select bits TBR2–TBR0. When the timebase counter chain rolls over, the TBIF flag is set. If the TBIE
bit is set, enabling the timebase interrupt, the counter chain overflow will generate a CPU interrupt
request.
Interrupts must be acknowledged by writing a 1 to the TACK bit.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
151
Timebase Module (TBM)
TBON
128
÷2
64
8
÷2
32
÷2
16
÷2
TBMCLK
FROM ICG MODULE
÷2
÷2
TACK
÷2
TBR0
÷2
TBR1
÷2
÷ 32,768
÷2
÷ 8192
÷2
÷ 2048
÷2
TBR2
TBMINT
TBIF
000
TBIE
R
001
010
100
SEL
011
101
110
111
Figure 14-1. Timebase Block Diagram
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
152
Freescale Semiconductor
TBM Interrupt Rate
14.5 TBM Interrupt Rate
The interrupt rate is determined by the equation:
Divider
1
t TBMRATE = ------------------------ = --------------------f TBMCLK
f TBMRATE
where:
fTBMCLK = Frequency supplied from the internal clock generator (ICG) module
Divider = Divider value as determined by TBR2–TBR0 settings. See Table 14-1.
As an example, a clock source of 4.9152 MHz and the TBR2–TBR0 set to {011}, the divider tap is 128
and the interrupt rate calculates to 128/4.9152 x 106 = 26 µs.
Table 14-1. Timebase Divider Selection
TBR2
0
0
0
0
1
1
1
1
TBR1
0
0
1
1
0
0
1
1
TBR0
0
1
0
1
0
1
0
1
Divider Tap
32768
8192
2048
128
64
32
16
8
NOTE
Do not change TBR2–TBR0 bits while the timebase is enabled (TBON = 1).
14.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
14.6.1 Wait Mode
The timebase module remains active after execution of the WAIT instruction. In wait mode the timebase
register is not accessible by the CPU.
If the timebase functions are not required during wait mode, reduce the power consumption by stopping
the timebase before executing the WAIT instruction.
14.6.2 Stop Mode
The timebase module may remain active after execution of the STOP instruction if the internal clock
generator has been enabled to operate during stop mode through the OSCENINSTOP bit in the
configuration register. The timebase module can be used in this mode to generate a periodic wake up
from stop mode.
If the internal clock generator has not been enabled to operate in stop mode, the timebase module will
not be active during stop mode. In stop mode, the timebase register is not accessible by the CPU.
If the timebase functions are not required during stop mode, reduce power consumption by disabling the
timebase module before executing the STOP instruction.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
153
Timebase Module (TBM)
14.7 Timebase Control Register
The timebase has one register, the timebase control register (TBCR), which is used to enable the
timebase interrupts and set the rate.
Address: $001C
Bit 7
Read:
TBIF
Write:
Reset:
0
6
5
4
TBR2
TBR1
TBR0
0
0
0
= Unimplemented
3
2
1
Bit 0
TBIE
TBON
R
0
0
0
0
R
= Reserved
0
TACK
Figure 14-2. Timebase Control Register (TBCR)
TBIF — Timebase Interrupt Flag
This read-only flag bit is set when the timebase counter has rolled over.
1 = Timebase interrupt pending
0 = Timebase interrupt not pending
TBR2–TBR0 — Timebase Divider Selection Bits
These read/write bits select the tap in the counter to be used for timebase interrupts as shown in
Table 14-1.
NOTE
Do not change TBR2–TBR0 bits while the timebase is enabled (TBON = 1).
TACK— Timebase ACKnowledge Bit
The TACK bit is a write-only bit and always reads as 0. Writing a 1 to this bit clears TBIF, the timebase
interrupt flag bit. Writing a 0 to this bit has no effect.
1 = Clear timebase interrupt flag
0 = No effect
TBIE — Timebase Interrupt Enabled Bit
This read/write bit enables the timebase interrupt when the TBIF bit becomes set. Reset clears the
TBIE bit.
1 = Timebase interrupt is enabled.
0 = Timebase interrupt is disabled.
TBON — Timebase Enabled Bit
This read/write bit enables the timebase. Timebase may be turned off to reduce power consumption
when its function is not necessary. The counter can be initialized by clearing and then setting this bit.
Reset clears the TBON bit.
1 = Timebase is enabled.
0 = Timebase is disabled and the counter initialized to 0s.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
154
Freescale Semiconductor
Chapter 15
Timer Interface Module (TIM)
15.1 Introduction
This section describes the timer interface module (TIM). The TIM is a 2-channel timer that provides a
timing reference with input capture, output compare, and pulse-width modulation functions. Figure 15-2
is a block diagram of the TIM.
15.2 Features
Features include:
• Two input capture/output compare channels:
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
• Buffered and unbuffered pulse-width modulation (PWM) signal generation
• Programmable TIM clock input — 7-frequency internal bus clock prescaler selection
• Free-running or modulo up-counter operation
• Toggle either channel pin on overflow
• TIM counter stop and reset bits
15.3 Pin Name Conventions
The TIM shares two input/output (I/O) pins with two port A I/O pins. The full names of the TIM I/O pins are
listed in Table 15-1. The generic pin names appear in the text that follows.
Table 15-1. Pin Name Conventions
TIM Generic Pin Names:
Full TIM Pin Names:
TCH0
TCH1
PTA2/KBD2/TCH0
PTA3/KBD3/TCH1
15.4 Functional Description
Figure 15-2 shows the structure of the TIM. The central component of the TIM is the 16-bit TIM counter
that can operate as a free-running counter or a modulo up-counter. The TIM counter provides the timing
reference for the input capture and output compare functions. The TIM counter modulo registers, TMODH
and TMODL, control the modulo value of the TIM counter. Software can read the TIM counter value at
any time without affecting the counting sequence.
The two TIM channels are programmable independently as input capture or output compare channels.
Figure 15-3 summarizes the timer registers.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
155
Freescale Semiconductor
SECURITY
MODULE
USER FLASH — 7680 BYTES
COMPUTER OPERATING PROPERLY
MODULE
LOW-VOLTAGE INHIBIT
MODULE
MONITOR ROM — 295 BYTES
2-CHANNEL TIMER INTERFACE
MODULE
USER FLASH VECTOR SPACE — 36 BYTES
FLASH BURN-IN ROM — 1024 BYTES
INTERNAL CLOCK GENERATOR
MODULE
(SOFTWARE SELECTABLE)
KEYBOARD INTERRUPT
MODULE
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATION INTERFACE
MODULE
SYSTEM INTEGRATION
MODULE
IRQ
MODULE
IRQ1(1)
VDD
VSS
PROGRAMMABLE TIME BASE
MODULE
BREAK
MODULE
POWER
Notes:
1. Pin contains integrated pullup resistor
2. High-current source/sink pin
3. Pin contains software selectable pullup resistor if general function I/O pin is configured as input.
Figure 15-1. Block Diagram Highlighting TIM Block and Pins
DDRA
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
PTA0/KBD0(2), (3)
PTA1/KBD1(2), (3)
PTA2/KBD2/TCH0(2), (3)
PTA3/KBD3/TCH1(2), (3)
PTA4/KBD4(2), (3)
POWER-ON RESET
MODULE
CONTROL AND STATUS REGISTERS — 78 BYTES
USER RAM — 192 BYTES
PTB
ARITHMETIC/LOGIC
UNIT
DDRB
CPU
REGISTERS
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
PTB5/TxD
PTB6/(OSC1)(4)
PTB7/(OSC2)/RST(4)
PTA
M68HC08 CPU
Timer Interface Module (TIM)
156
INTERNAL BUS
Functional Description
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
INTERRUPT
LOGIC
16-BIT COMPARATOR
TMODH:TMODL
TOV0
ELS0B
CHANNEL 0
ELS0A
CH0MAX
PORT
LOGIC
PTA2/KBD2/TCH0
16-BIT COMPARATOR
TCH0H:TCH0L
CH0F
INTERRUPT
LOGIC
16-BIT LATCH
MS0A
CH0IE
MS0B
INTERNAL BUS
TOV1
ELS1B
CHANNEL 1
ELS1A
CH1MAX
PORT
LOGIC
PTA3/KBD3/TCH1
16-BIT COMPARATOR
TCH1H:TCH1L
CH1F
INTERRUPT
LOGIC
16-BIT LATCH
MS1A
CH1IE
Figure 15-2. TIM Block Diagram
Addr.
Register Name
Bit 7
6
5
TOIE
TSTOP
4
3
0
0
2
1
Bit 0
PS2
PS1
PS0
Timer Status and Control Read:
Register (TSC) Write:
See page 163. Reset:
TOF
0
0
1
0
0
0
0
0
Timer Counter Register High Read:
$0021
(TCNTH) Write:
See page 164. Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Timer Counter Register Low Read:
(TCNTL) Write:
See page 164. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
1
1
1
1
1
1
1
1
$0020
$0022
$0023
Timer Counter Modulo Read:
Register High (TMODH) Write:
See page 165. Reset:
0
TRST
= Unimplemented
Figure 15-3. TIM I/O Register Summary
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
157
Timer Interface Module (TIM)
Addr.
$0024
$0025
$0026
Register Name
Timer Counter Modulo Read:
Register Low (TMODL) Write:
See page 165. Reset:
Timer Channel 0 Status and Read:
Control Register (TSC0) Write:
See page 165. Reset:
Timer Channel 0 Register Read:
High (TCH0H) Write:
See page 168. Reset:
$0027
Timer Channel 0 Register Read:
Low (TCH0L) Write:
See page 168. Reset:
$0028
Timer Channel 1 Status and Read:
Control Register (TSC1) Write:
See page 165. Reset:
$0029
$002A
Timer Channel 1 Register Read:
High (TCH1H) Write:
See page 168. Reset:
Timer Channel 1 Register Read:
Low (TCH1L) Write:
See page 168. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
1
1
1
1
1
1
1
1
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
CH0F
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH1F
0
CH1IE
0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
= Unimplemented
Figure 15-3. TIM I/O Register Summary (Continued)
15.4.1 TIM Counter Prescaler
The TIM clock source can be one of the seven prescaler outputs. The prescaler generates seven clock
rates from the internal bus clock. The prescaler select bits, PS2–PS0, in the TIM status and control
register select the TIM clock source.
15.4.2 Input Capture
With the input capture function, the TIM can capture the time at which an external event occurs. When an
active edge occurs on the pin of an input capture channel, the TIM latches the contents of the TIM counter
into the TIM channel registers, TCHxH and TCHxL. The polarity of the active edge is programmable. Input
captures can generate TIM CPU interrupt requests.
15.4.3 Output Compare
With the output compare function, the TIM can generate a periodic pulse with a programmable polarity,
duration, and frequency. When the counter reaches the value in the registers of an output compare
channel, the TIM can set, clear, or toggle the channel pin. Output compares can generate TIM CPU
interrupt requests.
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Functional Description
15.4.4 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare pulses as described in 15.4.3
Output Compare. The pulses are unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIM channel registers.
An unsynchronized write to the TIM channel registers to change an output compare value could cause
incorrect operation for up to two counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new value prevents any compare during
that counter overflow period. Also, using a TIM overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIM may pass the new value before it is written.
Use these methods to synchronize unbuffered changes in the output compare value on channel x:
• When changing to a smaller value, enable channel x output compare interrupts and write the new
value in the output compare interrupt routine. The output compare interrupt occurs at the end of
the current output compare pulse. The interrupt routine has until the end of the counter overflow
period to write the new value.
• When changing to a larger output compare value, enable TIM overflow interrupts and write the new
value in the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the
current counter overflow period. Writing a larger value in an output compare interrupt routine (at
the end of the current pulse) could cause two output compares to occur in the same counter
overflow period.
15.4.5 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the
TCH0 pin. The TIM channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1.
The output compare value in the TIM channel 0 registers initially controls the output on the TCH0 pin.
Writing to the TIM channel 1 registers enables the TIM channel 1 registers to synchronously control the
output after the TIM overflows. At each subsequent overflow, the TIM channel registers (0 or 1) that
control the output are the 1s written to last. TSC0 controls and monitors the buffered output compare
function, and TIM channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the
channel 1 pin, TCH1, is available as a general-purpose I/O pin.
NOTE
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. User software should track
the currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered output compares.
15.4.6 Pulse-Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIM can generate a PWM
signal. The value in the TIM counter modulo registers determines the period of the PWM signal. The
channel pin toggles when the counter reaches the value in the TIM counter modulo registers. The time
between overflows is the period of the PWM signal.
As Figure 15-4 shows, the output compare value in the TIM channel registers determines the pulse width
of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIM
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Timer Interface Module (TIM)
to clear the channel pin on output compare if the state of the PWM pulse is logic 1. Program the TIM to
set the pin on overflow if the state of the PWM pulse is logic 0.
The value in the TIM counter modulo registers and the selected prescaler output determines the
frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIM counter modulo registers produces a PWM period of 256 times the internal bus
clock period if the prescaler select value is $000. See 15.8.1 TIM Status and Control Register.
The value in the TIM channel registers determines the pulse width of the PWM output. The pulse width of
an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIM channel registers
produces a duty cycle of 128/256 or 50 percent.
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PULSE
WIDTH
PTAx/TCH
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 15-4. PWM Period and Pulse Width
15.4.7 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as described in 15.4.6 Pulse-Width
Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new
pulse width value over the old value currently in the TIM channel registers.
An unsynchronized write to the TIM channel registers to change a pulse width value could cause incorrect
operation for up to two PWM periods. For example, writing a new value before the counter reaches the
old value but after the counter reaches the new value prevents any compare during that PWM period.
Also, using a TIM overflow interrupt routine to write a new, smaller pulse width value may cause the
compare to be missed. The TIM may pass the new value before it is written.
Use these methods to synchronize unbuffered changes in the PWM pulse width on channel x:
• When changing to a shorter pulse width, enable channel x output compare interrupts and write the
new value in the output compare interrupt routine. The output compare interrupt occurs at the end
of the current pulse. The interrupt routine has until the end of the PWM period to write the new
value.
• When changing to a longer pulse width, enable TIM overflow interrupts and write the new value in
the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the current PWM
period. Writing a larger value in an output compare interrupt routine (at the end of the current pulse)
could cause two output compares to occur in the same PWM period.
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Functional Description
in the event of software error or noise. Toggling on output compare also can
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
15.4.8 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the TCH0 pin.
The TIM channel registers of the linked pair alternately control the pulse width of the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1.
The TIM channel 0 registers initially control the pulse width on the TCH0 pin. Writing to the TIM channel 1
registers enables the TIM channel 1 registers to synchronously control the pulse width at the beginning
of the next PWM period. At each subsequent overflow, the TIM channel registers (0 or 1) that control the
pulse width are the 1s written to last. TSC0 controls and monitors the buffered PWM function, and TIM
channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin,
TCH1, is available as a general-purpose I/O pin.
NOTE
In buffered PWM signal generation, do not write new pulse width values to
the currently active channel registers. User software should track the
currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered PWM signals.
15.4.9 PWM Initialization
To ensure correct operation when generating unbuffered or buffered PWM signals, use this initialization
procedure:
1. In the TIM status and control register (TSC):
a. Stop the TIM counter by setting the TIM stop bit, TSTOP.
b. Reset the TIM counter and prescaler by setting the TIM reset bit, TRST.
2. In the TIM counter modulo registers (TMODH and TMODL), write the value for the required PWM
period.
3. In the TIM channel x registers (TCHxH and TCHxL), write the value for the required pulse width.
4. In TIM channel x status and control register (TSCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or 1:0 (for buffered output compare
or PWM signals) to the mode select bits, MSxB and MSxA. See Table 15-2.
b. Write 1 to the toggle-on-overflow bit, TOVx.
c. Write 1:0 (to clear output on compare) or 1:1 (to set output on compare) to the edge/level
select bits, ELSxB and ELSxA. The output action on compare must force the output to the
complement of the pulse width level. See Table 15-2.
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare can also
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
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Timer Interface Module (TIM)
5. In the TIM status control register (TSC), clear the TIM stop bit, TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIM
channel 0 registers (TCH0H and TCH0L) initially control the buffered PWM output. TIM status control
register 0 (TSCR0) controls and monitors the PWM signal from the linked channels.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIM overflows. Subsequent output
compares try to force the output to a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a 100
percent duty cycle output. See 15.8.4 TIM Channel Status and Control Registers.
15.5 Interrupts
These TIM sources can generate interrupt requests:
• TIM overflow flag (TOF) — The timer overflow flag (TOF) bit is set when the TIM counter reaches
the modulo value programmed in the TIM counter modulo registers. The TIM overflow interrupt
enable bit, TOIE, enables TIM overflow interrupt requests. TOF and TOIE are in the TIM status and
control registers.
• TIM channel flags (CH1F and CH0F) — The CHxF bit is set when an input capture or output
compare occurs on channel x. Channel x TIM CPU interrupt requests are controlled by the channel
x interrupt enable bit, CHxIE. Channel x TIM CPU interrupt requests are enabled when CHxIE = 1.
CHxF and CHxIE are in the TIM channel x status and control register.
15.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
15.6.1 Wait Mode
The TIM remains active after the execution of a WAIT instruction. In wait mode the TIM registers are not
accessible by the CPU. Any enabled CPU interrupt request from the TIM can bring the MCU out of wait
mode.
If TIM functions are not required during wait mode, reduce power consumption by stopping the TIM before
executing the WAIT instruction.
15.6.2 Stop Mode
The TIM is inactive after the execution of a STOP instruction. The STOP instruction does not affect
register conditions or the state of the TIM counter. TIM operation resumes when the MCU exits stop mode
after an external interrupt.
15.7 I/O Signals
Port A shares two of its pins with the TIM, PTA3/KBD3/TCH1 and PTA2/KBD2/TCH0. Each channel
input/output (I/O) pin is programmable independently as an input capture pin or an output compare pin.
TCH0 can be configured as buffered output compare or buffered PWM pins.
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I/O Registers
15.8 I/O Registers
These I/O registers control and monitor operation of the TIM:
• TIM status and control register (TSC)
• TIM control registers (TCNTH and TCNTL)
• TIM counter modulo registers (TMODH and TMODL)
• TIM channel status and control registers (TSC0 and TSC1)
• TIM channel registers (TCH0H and TCH0L, TCH1H and TCH1L)
15.8.1 TIM Status and Control Register
The TIM status and control register (TSC):
• Enables TIM overflow interrupts
• Flags TIM overflows
• Stops the TIM counter
• Resets the TIM counter
• Prescales the TIM counter clock
Address: $0020
Bit 7
Read:
TOF
Write:
0
Reset:
0
6
5
TOIE
TSTOP
0
1
4
3
0
0
TRST
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
= Unimplemented
Figure 15-5. TIM Status and Control Register (TSC)
TOF — TIM Overflow Flag Bit
This read/write flag is set when the TIM counter reaches the modulo value programmed in the TIM
counter modulo registers. Clear TOF by reading the TIM status and control register when TOF is set
and then writing a 0 to TOF. If another TIM overflow occurs before the clearing sequence is complete,
then writing 0 to TOF has no effect. Therefore, a TOF interrupt request cannot be lost due to
inadvertent clearing of TOF. Reset clears the TOF bit. Writing a 1 to TOF has no effect.
1 = TIM counter has reached modulo value.
0 = TIM counter has not reached modulo value.
TOIE — TIM Overflow Interrupt Enable Bit
This read/write bit enables TIM overflow interrupts when the TOF bit becomes set. Reset clears the
TOIE bit.
1 = TIM overflow interrupts enabled
0 = TIM overflow interrupts disabled
TSTOP — TIM Stop Bit
This read/write bit stops the TIM counter. Counting resumes when TSTOP is cleared. Reset sets the
TSTOP bit, stopping the TIM counter until software clears the TSTOP bit.
1 = TIM counter stopped
0 = TIM counter active
NOTE
Do not set the TSTOP bit before entering wait mode if the TIM is required
to exit wait mode.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Timer Interface Module (TIM)
TRST — TIM Reset Bit
Setting this write-only bit resets the TIM counter and the TIM prescaler. Setting TRST has no effect on
any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIM
counter is reset and always reads as 0. Reset clears the TRST bit.
1 = Prescaler and TIM counter cleared
0 = No effect
NOTE
Setting the TSTOP and TRST bits simultaneously stops the TIM counter at
a value of $0000.
PS2–PS0 — Prescaler Select Bits
These read/write bits select one of the seven prescaler outputs as the input to the TIM counter as
Table 15-2 shows. Reset clears the PS2–PS0 bits.
Table 15-2. Prescaler Selection
PS2–PS0
TIM Clock Source
000
Internal bus clock ÷1
001
Internal bus clock ÷ 2
010
Internal bus clock ÷ 4
011
Internal bus clock ÷ 8
100
Internal bus clock ÷ 16
101
Internal bus clock ÷ 32
110
Internal bus clock ÷ 64
111
Not available
15.8.2 TIM Counter Registers
The two read-only TIM counter registers (TCNTH and TCNTL) contain the high and low bytes of the value
in the TIM counter. Reading the high byte (TCNTH) latches the contents of the low byte (TCNTL) into a
buffer. Subsequent reads of TCNTH do not affect the latched TCNTL value until TCNTL is read. Reset
clears the TIM counter registers. Setting the TIM reset bit (TRST) also clears the TIM counter registers.
Register name and address:
Read:
TCNTH — $0021
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Write:
Reset:
Register name and address:
Read:
TCNTL — $0022
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 15-6. TIM Counter Registers (TCNTH and TCNTL)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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I/O Registers
15.8.3 TIM Counter Modulo Registers
The read/write TIM modulo registers (TMODH and TMODL) contain the modulo value for the TIM counter.
When the TIM counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIM
counter resumes counting from $0000 at the next timer clock. Writing to the high byte (TMODH) inhibits
the TOF bit and overflow interrupts until the low byte (TMODL) is written. Reset sets the TIM counter
modulo registers.
Register name and address:
Bit 7
Read:
Bit 15
Write:
Reset:
1
TMODH — $0023
6
5
Register name and address:
Bit 7
Read:
Bit 7
Write:
Reset:
1
TMODL — $0024
6
5
4
3
2
1
Bit 0
14
13
12
11
10
9
Bit 8
1
1
1
1
1
1
1
4
3
2
1
Bit 0
6
5
4
3
2
1
Bit 0
1
1
1
1
1
1
1
Figure 15-7. TIM Counter Modulo Registers (TMODH and TMODL)
NOTE
Reset the TIM counter before writing to the TIM counter modulo registers.
15.8.4 TIM Channel Status and Control Registers
Each of the TIM channel status and control registers (TSC0 and TSC1):
• Flags input captures and output compares
• Enables input capture and output compare interrupts
• Selects input capture, output compare, or PWM operation
• Selects high, low, or toggling output on output compare
• Selects rising edge, falling edge, or any edge as the active input capture trigger
• Selects output toggling on TIM overflow
• Selects 0 percent and100 percent PWM duty cycle
• Selects buffered or unbuffered output compare/PWM operation
Register name and address: TSC0 — $0025
Bit 7
6
5
Read:
CH0F
CH0IE
MS0B
Write:
0
Reset:
0
0
0
Register name and address: TSC1 — $0028
Bit 7
6
5
Read:
CH1F
0
CH1IE
Write:
0
Reset:
0
0
0
= Unimplemented
4
3
2
1
Bit 0
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
Figure 15-8. TIM Channel Status and Control Registers (TSCO and TSC1)
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Timer Interface Module (TIM)
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set when an active edge occurs on
the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the
TIM counter registers matches the value in the TIM channel x registers.
When TIM CPU interrupt requests are enabled (CHxIE = 1), clear CHxF by reading TIM channel x
status and control register with CHxF set and then writing a 0 to CHxF. If another interrupt request
occurs before the clearing sequence is complete, then writing 0 to CHxF has no effect. Therefore, an
interrupt request cannot be lost due to inadvertent clearing of CHxF.
Reset clears the CHxF bit. Writing a 1 to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIM CPU interrupts on channel x. Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests
0 = Channel x CPU interrupt requests disabled
MS0B — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation. MS0B exists only in the TIM
channel 0 status and control register.
Setting MS0B disables the channel 1 status and control register and reverts TCH1 to general-purpose
I/O. Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture operation or unbuffered output
compare/PWM operation. See Table 15-3.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level of the TCHx pin. See Table 15-3.
Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE
Before changing a channel function by writing to the MS0B or MSxA bit, set
the TSTOP and TRST bits in the TIM status and control register (TSC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits control the active edge-sensing logic
on channel x.
When channel x is an output compare channel, ELSxB and ELSxA control the channel x output
behavior when an output compare occurs.
When ELSxB and ELSxA are both clear, channel x is not connected to port A, and pin PTAx/TCHx is
available as a general-purpose I/O pin. Table 15-3 shows how ELSxB and ELSxA work. Reset clears
the ELSxB and ELSxA bits.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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I/O Registers
Table 15-3. Mode, Edge, and Level Selection
MSxB
MSxA
ELSxB
ELSxA
Mode
Configuration
X
0
0
0
X
1
0
0
0
0
0
1
0
0
1
0
0
0
1
1
Capture on rising or falling edge
0
1
0
0
Software compare only
0
1
0
1
0
1
1
0
0
1
1
1
X
0
1
X
1
0
1
X
1
1
Output preset
Pin under port control; initial output level high
Pin under port control; initial output level low
Capture on rising edge only
Input capture
Capture on falling edge only
Output compare
or PWM
Toggle output on compare
1
Set output on compare
1
Buffered output
compare or
buffered PWM
Toggle output on compare
Clear output on compare
Clear output on compare
Set output on compare
NOTE
Before enabling a TIM channel register for input capture operation, make
sure that the PTAx/TCHx pin is stable for at least two bus clocks.
TOVx — Toggle On Overflow Bit
When channel x is an output compare channel, this read/write bit controls the behavior of the channel
x output when the TIM counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIM counter overflow.
0 = Channel x pin does not toggle on TIM counter overflow.
NOTE
When TOVx is set, a TIM counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx bit is at 1 and clear output on compare is selected, setting the CHxMAX bit forces the
duty cycle of buffered and unbuffered PWM signals to 100 percent. As Figure 15-9 shows, the
CHxMAX bit takes effect in the cycle after it is set or cleared. The output stays at 100 percent duty
cycle level until the cycle after CHxMAX is cleared.
NOTE
The PWM 0 percent duty cycle is defined as output low all of the time. To
generate the 0 percent duty cycle, select clear output on compare and then
clear the TOVx bit (CHxMAX = 0). The PWM 100 percent duty cycle is
defined as output high all of the time. To generate the 100 percent duty
cycle, use the CHxMAX bit in the TSCx register.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Timer Interface Module (TIM)
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTAx/TCH
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
Figure 15-9. CHxMAX Latency
15.8.5 TIM Channel Registers
These read/write registers (TCH0H/L and TCH1H/L) contain the captured TIM counter value of the input
capture function or the output compare value of the output compare function. The state of the TIM channel
registers after reset is unknown.
In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the TIM channel x registers (TCHxH)
inhibits input captures until the low byte (TCHxL) is read.
In output compare mode (MSxB:MSxA ≠ 0:0), writing to the high byte of the TIM channel x registers
(TCHxH) inhibits output compares until the low byte (TCHxL) is written.
Register name and address:
Read:
Write:
TCH0H — $0026
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Register name and address:
Read:
Write:
TCH0L — $0027
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Reset:
Indeterminate after reset
Register name and address:
Read:
Write:
TCH1H — $0029
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Register name and address:
Read:
Write:
Reset:
TCH1L — $002A
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 15-10. TIM Channel Registers (TCH0H/L and TCH1H/L)
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
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Chapter 16
Development Support
16.1 Introduction
This section describes the break module, the monitor read-only memory (MON), and the monitor mode
entry methods.
16.2 Break Module (BRK)
The break module can generate a break interrupt that stops normal program flow at a defined address to
enter a background program.
Features include:
• Accessible input/output (I/O) registers during the break interrupt
• Central processor unit (CPU) generated break interrupts
• Software generated break interrupts
• Computer operating properly (COP) disabling during break interrupts
16.2.1 Functional Description
When the internal address bus matches the value written in the break address registers, the break module
issues a breakpoint signal to the CPU. The CPU then loads the instruction register with a software
interrupt instruction (SWI) after completion of the current CPU instruction. The program counter vectors
to $FFFC and $FFFD ($FEFC and $FEFD in monitor mode).
These events can cause a break interrupt to occur:
• A CPU-generated address (the address in the program counter) matches the contents of the break
address registers.
• Software writes a 1 to the BRKA bit in the break status and control register.
When a CPU-generated address matches the contents of the break address registers, the break interrupt
begins after the CPU completes its current instruction. A return-from-interrupt instruction (RTI) in the
break routine ends the break interrupt and returns the MCU to normal operation. Figure 16-1 shows the
structure of the break module.
16.2.1.1 Flag Protection During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during
the break state.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
169
Development Support
IAB15–IAB8
BREAK ADDRESS REGISTER HIGH
8-BIT COMPARATOR
IAB15–IAB0
CONTROL
BREAK
8-BIT COMPARATOR
BREAK ADDRESS REGISTER LOW
IAB7–IAB0
Figure 16-1. Break Module Block Diagram
Addr.
$FE00
$FE03
Register Name
SIM Break Status Register Read:
(SBSR) Write:
See page 172. Reset:
SIM Break Flag Control Read:
Register (SBFCR) Write:
See page 173. Reset:
Break Address Register High Read:
$FE09
(BRKH) Write:
See page 172. Reset:
Break Address Register Low Read:
$FE0A
(BRKL) Write:
See page 172. Reset:
$FE0B
Break Status and Control Read:
Register (BRKSCR) Write:
See page 171. Reset:
$FE02
Break Auxiliary Register Read:
(BRKAR) Write:
See page 173. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
1
0
0
BW
0
R
R
R
R
R
R
NOTE
R
0
0
0
1
0
0
0
0
BCFE
R
R
R
R
R
R
R
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
BRKE
BRKA
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
R
= Reserved
0
Note: Writing a 0 clears BW.
= Unimplemented
BDCOP
0
Figure 16-2. I/O Register Summary
16.2.1.2 CPU During Break Interrupts
The CPU starts a break interrupt by:
• Loading the instruction register with the SWI instruction
• Loading the program counter with $FFFC and $FFFD ($FEFC and $FEFD in monitor mode)
The break interrupt begins after completion of the CPU instruction in progress. If the break address
register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
170
Freescale Semiconductor
Break Module (BRK)
16.2.1.3 TIM1 and TIM2 During Break Interrupts
A break interrupt stops the timer counters.
16.2.1.4 COP During Break Interrupts
The COP is disabled during a break interrupt when BDCOP bit is set in break auxiliary register (BRKAR).
16.2.2 Break Module Registers
These registers control and monitor operation of the break module:
• Break status and control register (BRKSCR)
• Break address register high (BRKH)
• Break address register low (BRKL)
• SIM break status register (SBSR)
• SIM break flag control register (SBFCR)
16.2.2.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module enable and status bits.
Address:
$FE0B
Bit 7
Read:
Write:
Reset:
6
BRKE
BRKA
0
0
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 16-3. Break Status and Control Register (BRKSCR)
BRKE — Break Enable Bit
This read/write bit enables breaks on break address register matches. Clear BRKE by writing a 0 to
bit 7. Reset clears the BRKE bit.
1 = Breaks enabled on 16-bit address match
0 = Breaks disabled on 16-bit address match
BRKA — Break Active Bit
This read/write status and control bit is set when a break address match occurs. Writing a 1 to BRKA
generates a break interrupt. Clear BRKA by writing a 0 to it before exiting the break routine. Reset
clears the BRKA bit.
1 = When read, break address match
0 = When read, no break address match
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
171
Development Support
16.2.2.2 Break Address Registers
The break address registers (BRKH and BRKL) contain the high and low bytes of the desired breakpoint
address. Reset clears the break address registers.
Address:
Read:
Write:
Reset:
$FE09
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Figure 16-4. Break Address Register High (BRKH)
Address:
Read:
Write:
Reset:
$FE0A
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Figure 16-5. Break Address Register Low (BRKL)
16.2.2.3 Break Status Register
The break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode.
The flag is useful in applications requiring a return to wait mode after exiting from a break interrupt.
Address:
$FE00
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
1
0
0
BW
0
Write:
R
R
R
R
R
R
NOTE
R
Reset:
0
0
0
1
0
0
0
0
R
= Reserved
Note: Writing a 0 clears BW.
Figure 16-6. SIM Break Status Register (SBSR)
BW — Break Wait Bit
This read/write bit is set when a break interrupt causes an exit from wait mode. Clear BW by writing
a 0 to it. Reset clears BW.
1 = Break interrupt during wait mode
0 = No break interrupt during wait mode
BW can be read within the break interrupt routine. The user can modify the return address on the stack
by subtracting 1 from it.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
172
Freescale Semiconductor
Break Module (BRK)
16.2.2.4 Break Flag Control Register
The break flag control register (SBFCR) contains a bit that enables software to clear status bits while the
MCU is in a break state.
Address:
$FE03
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
0
R
= Reserved
Figure 16-7. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing status registers while the MCU is
in a break state. To clear status bits during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
16.2.2.5 Break Auxiliary Register
The break auxiliary register (BRKAR) contains a bit that enables software to disable the COP while the
MCU is in a state of break interrupt with monitor mode.
Address:
$FE02
Read:
Bit 7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Write:
Reset:
Bit 0
BDCOP
0
= Unimplemented
Figure 16-8. Break Auxiliary Register (BRKAR)
BDCOP — Break Disable COP Bit
This read/write bit disables the COP during a break interrupt. Reset clears the BDCOP bit.
1 = COP disabled during break interrupt
0 = COP enabled during break interrupt
16.2.3 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
16.2.3.1 Wait Mode
If enabled, the break module is active in wait mode. In the break routine, the user can subtract one from
the return address on the stack if SBSW is set. Clear the BW bit by writing 0 to it.
16.2.3.2 Stop Mode
A break interrupt causes exit from stop mode and sets the BW bit in the break status register.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
173
Development Support
16.3 Monitor ROM (MON)
The monitor ROM allows complete testing of the microcontroller unit (MCU) through a single-wire
interface with a host computer. Monitor mode entry can be achieved without use of the higher test voltage,
VTST, as long as vector addresses $FFFE and $FFFF are blank, thus reducing hardware requirements for
in-circuit programming.
Features include:
• Normal user-mode pin functionality
• One pin dedicated to serial communication between monitor ROM and host computer
• Standard mark/space non-return-to-zero (NRZ) communication with host computer
• Execution of code in random-access memory (RAM) or FLASH
• FLASH memory security(1)
• FLASH memory programming interface
• Monitor mode entry without high voltage, VTST, if reset vector is blank ($FFFE and $FFFF contain
$FF)
• Standard monitor mode entry if high voltage, VTST, is applied to IRQ
16.3.1 Functional Description
The monitor ROM receives and executes commands from a host computer via a standard RS-232
interface. Simple monitor commands can access any memory address. In monitor mode, the
microcontroller unit (MCU) can execute host-computer code in RAM while all MCU pins retain normal
operating mode functions. All communication between the host computer and the MCU is through the
PTA0 pin. A level-shifting and multiplexing interface is required between PTA0 and the host computer.
PTA0 is used in a wired-OR configuration and requires a pullup resistor.
16.3.1.1 Monitor Mode Entry
There are two methods for entering monitor mode. The first is the traditional M68HC08 method where
VTST is applied to IRQ1 and the mode pins are configured appropriately. A second method, intended for
in-circuit programming applications, will force entry into monitor mode without requiring high voltage on
the IRQ1 pin when the reset vector locations of the FLASH are erased ($FF).
Both of these methods require that the PTA1 pin be pulled low for the first 24 CGMXCLK cycles after the
part comes out of reset. This check is used by the monitor code to configure the MCU for serial
communication.
16.3.1.2 Normal Monitor Mode
Normal monitor mode is useful for MCU evaluation, factory testing, and development tool programming
operation. Figure 16-9 shows an example circuit used for normal monitor mode. Table 16-1 shows the pin
conditions for entering this mode.
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
174
Freescale Semiconductor
Monitor ROM (MON)
VDD
68HC908KX8
10 kΩ
RST (PTB7/OSC2)
0.1 µF
VTST
1 kΩ
IRQ1
1
10 µF
10 µF
MC145407
+
20
+
3
18
4
17
DB-25
2
2
19
5
16
10 µF
VDD
OSC1
VDD
7
VDD
14
MC74HC125
15
6
VSS
9.8304-MHz
CANNED
OSCILLATOR
0.1 µF
1
3
VDD
10 µF
0.1 µF
+
+
VDD
2
3
6
5
10 kΩ
PTA0
4
PTB1 (PTXMOD1)
7
VDD
10 kΩ
PTB0 (PTXMOD0)
PTA1 (SERIAL SELECT)
Figure 16-9. Normal Monitor Mode Circuit
Table 16-1. Monitor Mode Entry
$FFFE/
$FFFF
IRQ1
Pin
PTB1 Pin
(PTXMOD1)
PTB0 Pin
(PTXMOD0)
PTA1
Pin
PTA0
Pin
CGMOUT
Bus
Frequency
(fOP)
X
VTST
0
1
0
1
CGMXCLK
----------------------------2
CGMOUT
-------------------------2
$FF
blank
VDD
X
X
0
1
CGMXCLK
----------------------------2
CGMOUT
-------------------------2
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
175
Development Support
NOTE
PTA1 = 0 and PTA0 = 1 allow normal serial communications. PTA1 = 1
allows parallel communications during security code entry. (For parallel
communications, configure PTA0 = 0 or PTA0 = 1.)
The MCU initially comes out of reset using the external clock for its clock source. This overrides the user
mode operation of the oscillator circuits where the part comes up using the internally generated oscillator.
Running from an external clock allows the MCU, using an appropriate frequency clock source, to
communicate with host software at standard baud rates.
NOTE
While the voltage on IRQ1 is at VTST, the ICG module is bypassed and the
external square-wave clock becomes the clock source. Dropping IRQ1 to
below VTST will remove the bypass and the MCU will revert to the clock
source selected by the ICG (as determined by the settings in the ICG
registers).
In normal monitor mode with VTST on IRQ1, the MCU alters
PTB7/(OSC2)/RST to function as a RST pin. This is useful for testing the
MCU. Dropping IRQ1 voltage to below VTST will revert PTB7/(OSC2)/RST
to its user mode function.
The computer operating properly (COP) module is disabled in normal monitor mode whenever VTST is
applied to the IRQ1 pin. If the voltage on IRQ1 is less than VTST, the COP module is controlled by the
COPD configuration bit.
16.3.1.3 Forced Monitor Mode
If the voltage applied to the IRQ1 is less than VTST, the MCU will come out of reset in user mode. The
MENRST module is monitoring the reset vector fetches and will assert an internal reset if it detects that
the reset vectors are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode
without requiring high voltage on the IRQ1 pin.
Once out of reset, the monitor code is initially executing off the internal clock at its default frequency. The
monitor code reconfigures the ICG module to use the external square-wave clock source. Switching to an
external clock source allows the MCU, using an appropriate clock frequency, to communicate with host
software at standard baud rates.
The COP module is disabled in forced monitor mode. Any reset other than a power-on reset (POR) will
automatically force the MCU to come back to the forced monitor mode.
16.3.1.4 Monitor Mode Vectors
Monitor mode uses alternate vectors for reset and SWI interrupts. The alternate vectors are in the $FE
page instead of the $FF page and allow code execution from the internal monitor firmware instead of user
code. Table 16-2 shows vector differences between user mode and monitor mode.
Table 16-2. Monitor Mode Vector Relocation
Modes
Reset Vector High
Reset Vector Low
SWI Vector High
SWI Vector Low
User
$FFFE
$FFFF
$FFFC
$FFFD
Monitor
$FEFE
$FEFF
$FEFC
$FEFD
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
176
Freescale Semiconductor
Monitor ROM (MON)
16.3.1.5 Data Format
The MCU waits for the host to send eight security bytes (see 16.3.2 Security). After the security bytes, the
MCU sends a break signal (10 consecutive 0s) to the host computer, indicating that it is ready to receive
a command.
Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format.
Transmit and receive baud rates must be identical.
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
NEXT
START
BIT
Figure 16-10. Monitor Data Format
16.3.1.6 Break Signal
A start bit (0) followed by nine 0 bits is a break signal. When the monitor receives a break signal, it drives
the PTA0 pin high for the duration of two bits and then echoes back the break signal.
MISSING STOP BIT
2-STOP BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 16-11. Break Transaction
16.3.1.7 Baud Rate
The communication baud rate is controlled by the CGMXCLK frequency output of the internal clock
generator module.
16.3.1.8 Force Monitor Mode
In forced monitor mode, the baud rate is fixed at CGMXCLK/1024. A CMGXCLK frequency of 4.9152 MHz
results in a 4800 baud rate. A 9.8304-MHz frequency produces a 9600 baud rate.
16.3.1.9 Normal Monitor Mode
In normal monitor mode, the communication baud rate is controlled by the CGMXCLK frequency output
of the internal clock generator module. Table 16-3 lists CGMXCLK frequencies required to achieve
standard baud rates. Other standard baud rates can be accomplished using other clock frequencies. The
internal clock can be used as the clock source by programming the internal clock generator registers
however, monitor mode will always be entered using the external clock as the clock source.
Table 16-3. Normal Monitor Mode Baud Rate Selection
CGMXCLK Frequency (MHz)
Baud Rate
9.8304
9600
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
177
Development Support
16.3.1.10 Commands
The monitor ROM firmware uses these commands:
• READ, read memory
• WRITE, write memory
• IREAD, indexed read
• IWRITE, indexed write
• READSP, read stack pointer
• RUN, run user program
The monitor ROM firmware echoes each received byte back to the PTA0 pin for error checking. An 11-bit
delay at the end of each command allows the host to send a break character to cancel the command. A
delay of two bit times occurs before each echo and before READ, IREAD, or READSP data is returned.
The data returned by a read command appears after the echo of the last byte of the command.
NOTE
Wait one bit time after each echo before sending the next byte.
FROM
HOST
READ
ADDRESS ADDRESS ADDRESS ADDRESS
HIGH
HIGH
LOW
LOW
4
1
4
1
READ
4
1
DATA
4
3, 2
ECHO
Notes:
1 = Echo delay, 2 bit times
2 = Data return delay, 2 bit times
3 = Cancel command delay, 11 bit times
4 = Wait 1 bit time before sending next byte.
RETURN
Figure 16-12. Read Transaction
FROM
HOST
4
ADDRESS
HIGH
WRITE
WRITE
1
4
ADDRESS ADDRESS ADDRESS
HIGH
LOW
LOW
1
4
1
DATA
4
DATA
1
3, 4
ECHO
Notes:
1 = Echo delay, 2 bit times
3 = Cancel command delay, 11 bit times
4 = Wait 1 bit time before sending next byte.
Figure 16-13. Write Transaction
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
178
Freescale Semiconductor
Monitor ROM (MON)
A brief description of each monitor mode command is given in Table 16-4 through Table 16-9.
Table 16-4. READ (Read Memory) Command
Description
Read byte from memory
Operand
2-byte address in high-byte:low-byte order
Data Returned
Returns contents of specified address
Opcode
$4A
Command Sequence
SENT TO MONITOR
READ
ADDRESS
HIGH
READ
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
ECHO
RETURN
Table 16-5. WRITE (Write Memory) Command
Description
Operand
Data Returned
Opcode
Write byte to memory
2-byte address in high-byte:low-byte order; low byte followed by data byte
None
$49
Command Sequence
FROM HOST
WRITE
ADDRESS
HIGH
WRITE
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
DATA
ECHO
Table 16-6. IREAD (Indexed Read) Command
Description
Operand
Data Returned
Opcode
Read next 2 bytes in memory from last address accessed
2-byte address in high byte:low byte order
Returns contents of next two addresses
$1A
Command Sequence
FROM HOST
IREAD
ECHO
IREAD
DATA
DATA
RETURN
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
179
Development Support
Table 16-7. IWRITE (Indexed Write) Command
Description
Write to last address accessed + 1
Operand
Single data byte
Data Returned
Opcode
None
$19
Command Sequence
FROM HOST
IWRITE
IWRITE
DATA
DATA
ECHO
A sequence of IREAD or IWRITE commands can access a block of memory sequentially over the full
64-Kbyte memory map.
Table 16-8. READSP (Read Stack Pointer) Command
Description
Operand
Data Returned
Opcode
Reads stack pointer
None
Returns incremented stack pointer value (SP + 1) in high-byte:low-byte order
$0C
Command Sequence
FROM HOST
READSP
SP
HIGH
READSP
ECHO
SP
LOW
RETURN
Table 16-9. RUN (Run User Program) Command
Description
Executes PULH and RTI instructions
Operand
None
Data Returned
None
Opcode
$28
Command Sequence
FROM HOST
RUN
RUN
ECHO
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
180
Freescale Semiconductor
Monitor ROM (MON)
The MCU executes the SWI and PSHH instructions when it enters monitor mode. The RUN command
tells the MCU to execute the PULH and RTI instructions. Before sending the RUN command, the host can
modify the stacked CPU registers to prepare to run the host program. The READSP command returns
the incremented stack pointer value, SP + 1. The high and low bytes of the program counter are at
addresses SP + 5 and SP + 6.
SP
HIGH BYTE OF INDEX REGISTER
SP + 1
CONDITION CODE REGISTER
SP + 2
ACCUMULATOR
SP + 3
LOW BYTE OF INDEX REGISTER
SP + 4
HIGH BYTE OF PROGRAM COUNTER
SP + 5
LOW BYTE OF PROGRAM COUNTER
SP + 6
SP + 7
Figure 16-14. Stack Pointer at Monitor Mode Entry
16.3.2 Security
A security feature discourages unauthorized reading of FLASH locations while in monitor mode. The host
can bypass the security feature at monitor mode entry by sending eight security bytes that match the
bytes at locations $FFF6–$FFFD. Locations $FFF6–$FFFD contain user-defined data.
NOTE
Do not leave locations $FFF6–$FFFD blank. For security reasons, program
locations $FFF6–$FFFD even if they are not used for vectors. If FLASH is
erased, the eight security byte values to be sent to the MCU are $FF, the
unprogrammed state of the FLASH.
During monitor mode entry, a reset must be asserted. PTA1 must be held low during the reset and 24
CGMXCLK cycles after the end of the reset. Then the MCU will wait for eight security bytes on PTA0.
Each byte will be echoed back to the host. See Figure 16-15.
If the received bytes match those at locations $FFF6–$FFFD, the host bypasses the security feature and
can read all FLASH locations and execute code from FLASH. Security remains bypassed until a reset
occurs. After any reset, security will be locked. To bypass security again, the host must resend the eight
security bytes on PTA0.
If the received bytes do not match the data at locations $FFF6–$FFFD, the host fails to bypass the
security feature. The MCU remains in monitor mode, but reading FLASH locations returns undefined data,
and trying to execute code from FLASH causes an illegal address reset.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
181
Development Support
VDD
4096 + 64 CGMXCLK CYCLES
IRST
24 CGMXCLK CYCLES
PTA1
COMMAND
BYTE 8
BYTE 2
BYTE 1
256 CGMXCLK CYCLES (ONE BIT TIME)
FROM HOST
PTA0
4
1
BREAK
2
COMMAND ECHO
1
BYTE 8 ECHO
BYTE 1 ECHO
FROM MCU
1
BYTE 2 ECHO
4
1
Notes: 1 = Echo delay (2 bit times)
2 = Data return delay (2 bit times)
4 = Wait 1 bit time before sending next byte.
Figure 16-15. Monitor Mode Entry Timing
After receiving the eight security bytes from the host, the MCU transmits a break character signalling that
it is ready to receive a command.
NOTE
The MCU does not transmit a break character until after the host sends the
eight security bytes.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
182
Freescale Semiconductor
Chapter 17
Electrical Specifications
17.1 Introduction
This section contains electrical and timing specifications.
17.2 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the microcontroller unit (MCU) can be exposed without
permanently damaging it.
NOTE
This device is not guaranteed to operate properly at the maximum ratings.
Refer to 17.5 5.0-Vdc DC Electrical Characteristics, and for guaranteed
operating conditions.
Characteristic(1)
Symbol
Value
Unit
Supply voltage
VDD
–0.3 to +6.0
V
Input voltage
VIn
VSS –0.3 to VDD +0.3
V
I
±15
mA
IPTA0–IPTA4
±25
mA
Maximum current out of VSS
IMVSS
100
mA
Maximum current into VDD
IMVDD
100
mA
Storage temperature
TSTG
–55 to +150
°C
Maximum current per pin
Excluding VDD, VSS, and PTA0–PTA4
Maximum current for pins
PTA0–PTA4
1. Voltages referenced to VSS
NOTE
This device contains circuitry to protect the inputs against damage due to
high static voltages or electric fields; however, it is advised that normal
precautions be taken to avoid application of any voltage higher than
maximum-rated voltages to this high-impedance circuit. For proper
operation, it is recommended that VIn and VOut be constrained to the range
VSS ≤ (VIn or VOut) ≤ VDD. Reliability of operation is enhanced if unused
inputs are connected to an appropriate logic voltage level (for example,
either VSS or VDD).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
183
Electrical Specifications
17.3 Functional Operating Range
Characteristic
Symbol
Value
Unit
TA
–40 to 125
°C
VDD
3.0 ± 10%
5.0 ± 10%
V
Symbol
Value
Unit
Thermal resistance
PDIP (16 pins)
SOIC (16 pins)
θJA
66
95
°C/W
I/O pin power dissipation
PI/O
User determined
W
Power dissipation(1)
PD
PD = (IDD x VDD) + PI/O =
K/(TJ + 273°C)
W
Constant(2)
K
Average junction temperature
Operating temperature range
Operating voltage range
17.4 Thermal Characteristics
Characteristic
Maximum junction temperature
PD x (TA + 273°C)
+ PD2 x θJA
W/°C
TJ
TA + (PD x θJA)
°C
TJM
135
°C
1. Power dissipation is a function of temperature.
2. K is a constant unique to the device. K can be determined for a known TA and measured PD. With this value of K, PD and
TJ can be determined for any value of TA.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
184
Freescale Semiconductor
5.0-Vdc DC Electrical Characteristics
17.5 5.0-Vdc DC Electrical Characteristics
Characteristic(1)
Symbol
Min
Typ(2)
Max
VDD –0.4
VDD –1.5
VDD –0.8
—
—
—
—
—
—
—
—
—
—
—
—
0.4
1.5
0.8
Unit
Output high voltage
ILoad = –2.0 mA, all I/O pins
ILoad = –10.0 mA, all I/O pins
ILoad = –15.0 mA, PTA0–PTA4 only
VOH
Output low voltage
ILoad = 1.6 mA, all I/O pins
ILoad = 10.0 mA, all I/O pins
ILoad = 15.0 mA, PTA0–PTA4 only
VOL
Input high voltage — all ports, IRQ1
VIH
0.7 x VDD
—
VDD + 0.3
V
Input low voltage — all ports, IRQ1
VIL
VSS
—
0.3 x VDD
V
—
—
—
15
2.2
0.8
25
5
1.75
mA
mA
µA
V
V
VDD supply current
Run(3), (4)
Wait(4), (5)
Stop, 25°C(6)
IDD
I/O ports Hi-Z leakage current(7)
IIL
–10
—
+10
µA
Input current
IIn
–10
—
+10
µA
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
POR rearm voltage(8)
VPOR
0
—
100
mV
POR reset voltage(9)
VPOR
0
700
800
mV
POR rise time ramp rate
RPOR
0.035
—
—
V/ms
Monitor mode entry voltage
VTST
VDD+ 2.5
VDD+ 4.0
V
Low-voltage inhibit reset, trip falling voltage
VTRIPF
3.90
4.25
4.50
V
Low-voltage inhibit reset, trip rising voltage
VTRIPR
4.20
4.35
4.60
V
Low-voltage inhibit reset/recover hysteresis
VHYS
—
100
—
mV
Pullup resistor
PTA0–PTA4, IRQ1
RPU
24
—
48
kΩ
1. VDD = 5.5 Vdc to 4.5 Vdc, VSS = 0 Vdc, TA = –40°C to +125°C, unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using internal oscillator at its 32-MHz rate. VDD = 5.5 Vdc. All inputs 0.2 V from rail. No dc
loads. Less than 100 pF on all outputs. All ports configured as inputs. Measured with all modules enabled.
4. All measurements taken with LVI enabled.
5. Wait IDD measured using internal oscillator at its 1-MHz rate. All inputs 0.2 V from rail; no dc loads; less than 100 pF on all
outputs. All ports configured as inputs.
6. Stop IDD is measured with no port pin sourcing current; all modules are disabled. OSCSTOPEN option is not selected.
7. Pullups and pulldowns are disabled.
8. Maximum is highest voltage that POR is guaranteed.
9. Maximum is highest voltage that POR is possible.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
185
Electrical Specifications
17.6 3.0-Vdc DC Electrical Characteristics
Characteristic(1)
Symbol
Min
Typ(2)
Max
VDD –0.3
VDD –1.0
VDD –0.6
—
—
—
—
—
—
—
—
—
—
—
—
0.3
1.0
0.6
V
V
V
Unit
Output high voltage
ILoad = –0.6 mA, all I/O pins
ILoad = –4.0 mA, all I/O pins
ILoad = –10 mA, PTA0–PTA4 only
VOH
Output low voltage
ILoad = 0.5 mA, all I/O pins
ILoad = 6.0 mA, all I/O pins
ILoad = 10 mA, PTA0–PTA4 only
VOL
Input high voltage — all ports, IRQ1
VIH
0.7 x VDD
—
VDD + 0.3
V
Input low voltage — all ports, IRQ1
VIL
VSS
—
0.3 x VDD
V
—
—
—
5
1
0.65
10
2.5
1.25
mA
mA
µA
V
VDD supply current
Run(3), (4)
Wait(4), (5)
Stop, 25°C(6)
IDD
I/O ports Hi-Z leakage current(7)
IIL
–10
—
+10
µA
Input current
IIn
–10
—
+10
µA
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
POR rearm voltage(8)
VPOR
0
—
100
mV
POR reset voltage(9)
VPOR
0
700
800
mV
POR rise time ramp rate
RPOR
0.02
—
—
V/ms
Monitor mode entry voltage
VTST
VDD+ 2.5
—
VDD+ 4.0
V
Low-voltage inhibit reset, trip falling voltage
VTRIPF
2.45
2.60
2.70
V
Low-voltage inhibit reset, trip rising voltage
VTRIPR
2.55
2.66
2.80
V
Low-voltage inhibit reset/recover hysteresis
VHYS
—
60
—
mV
Pullup resistor
PTA0–PTA4, IRQ1
RPU
24
—
48
kΩ
1. VDD = 3.3 to 2.7 Vdc, VSS = 0 Vdc, TA = –40°C to +125°C, unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using internal oscillator at its 16-MHz rate. VDD = 3.3 Vdc. All inputs 0.2 V from rail. No dc
loads. Less than 100 pF on all outputs. All ports configured as inputs. Measured with all modules enabled.
4. All measurements taken with LVI enabled.
5. Wait IDD measured using internal oscillator at its 1 MHz rate. All inputs 0.2 V from rail; no dc loads; less than 100 pF on all
outputs. All ports configured as inputs.
6. Stop IDD is measured with no port pins sourcing current; all modules are disabled.
7. Pullups and pulldowns are disabled.
8. Maximum is highest voltage that POR is guaranteed.
9. Maximum is highest voltage that POR is possible.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
186
Freescale Semiconductor
Internal Oscillator Characteristics
17.7 Internal Oscillator Characteristics
Characteristic(1)
Internal oscillator base frequency(2), (3)
Internal oscillator tolerance
Symbol
Min
Typ
Max
Unit
fINTOSC
230.4
307.2
384
kHz
fOSC_TOL
–25
—
+25
%
N
1
—
127
—
Internal oscillator multiplier(4)
1. VDD = 5.5 Vdc to 2.7 Vdc, VSS = 0 Vdc, TA = –40°C to +125°C, unless otherwise noted
2. Internal oscillator is selectable through software for a maximum frequency. Actual frequency will be
multiplier (N) x base frequency.
3. fBus = (fINTOSC / 4) x N when internal clock source selected
4. Multiplier must be chosen to limit the maximum bus frequency of 4 MHz for 2.7-V operation and 8 MHz for 4.5-V operation.
17.8 External Oscillator Characteristics
Characteristic(1)
Symbol
Min
Typ
Max
dc(5)
—
32 M(6)
60
307.2 k
—
—
307.2 k
32 M(6)
Unit
External clock option(2), (3)
With ICG clock disabled
With ICG clock enabled
EXTSLOW = 1(4)
EXTSLOW = 0(4)
fEXTOSC
External crystal options(7), (8)
EXTSLOW = 1(4)
EXTSLOW = 0(4)
fEXTOSC
30 k
1M
—
—
100 k
8M
Hz
Crystal load capacitance(9)
CL
—
—
—
pF
Crystal fixed capacitance(9)
C1
—
2 x CL
—
pF
Crystal tuning capacitance(9)
C2
—
2 x CL
—
pF
Feedback bias resistor(9)
RB
—
10
—
MΩ
Series resistor (9), (10)
RS
—
—
—
MΩ
Hz
1.
2.
3.
4.
VDD = 5.5 to 2.7 Vdc, VSS = 0 Vdc, TA = –40°C to +125°C, unless otherwise noted
Setting EXTCLKEN configuration option enables OSC1 pin for external clock square-wave input.
No more than 10% duty cycle deviation from 50%
EXTSLOW configuration option configures external oscillator for a slow speed crystal and sets the clock monitor circuits
of the ICG module to expect an external clock frequency that is higher/lower than the internal oscillator base frequency,
fINTOSC.
5. Some modules may require a minimum frequency greater than dc for proper operation. See appropriate table for this
information.
6. MCU speed derates from 32 MHz at VDD = 4.5 Vdc to 16 MHz at VDD = 2.7 Vdc.
7. Setting EXTCLKEN and EXTXTALEN configuration options enables OSC1 and OSC2 pins for external crystal option.
8. fBus = (fEXTOSC / 4) when external clock source is selected.
9. Consult crystal vendor data sheet, see Figure 7-3. External Clock Generator Block Diagram.
10. Not required for high-frequency crystals
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
187
Electrical Specifications
17.9 Trimmed Accuracy of the Internal Clock Generator
The unadjusted frequency of the low-frequency base clock (IBASE), when the comparators in the
frequency comparator indicate zero error, can vary as much as ±25% due to process, temperature, and
voltage. The trimming capability exists to compensate for process affects. The remaining variation in
frequency is due to temperature, voltage, and change in target frequency (multiply register setting). These
affects are designed to be minimal, however variation does occur. Better performance is seen at 3 V and
lower settings of N.
17.9.1 2.7-Volt to 3.3-Volt Trimmed Internal Clock Generator Characteristics
Characteristic(1)
Symbol
Min
Typ
Max
Unit
Absolute trimmed internal oscillator tolerance(2), (3)
–40°C to 85°C
–40°C to 125°C
Fabs_tol
—
—
2.5
4.0
5.0
5.7
%
Variation over temperature(3), (4)
Var_temp
—
0.03
0.05
%/C
Variation over voltage(3), (5)
25°C
–40°C to 85°C
–40°C to 125°C
Var_volt
—
—
—
0.5
0.7
0.7
2.0
2.0
2.0
%/V
1. These specifications concern long-term frequency variation. Each measurement is taken over a 1-ms period.
2. Absolute value of variation in ICG output frequency, trimmed at nominal VDD and temperature, as temperature and VDD
are allowed to vary for a single given setting of N.
3. Specification is characterized but not tested.
4. Variation in ICG output frequency for a fixed N and voltage
5. Variation in ICG output frequency for a fixed N
17.9.2 4.5-Volt to 5.5-Volt Trimmed Internal Clock Generator Characteristics
Characteristic(1)
Symbol
Min
Typ
Max
Unit
Absolute trimmed internal oscillator tolerance(2), (3)
–40°C to 85°C
–40°C to 125°C
Fabs_tol
—
—
4.0
5.0
7.0
10.0
%
Variation over temperature(3), (4)
Var_temp
—
0.05
0.08
%/C
Variation over voltage(3), (5)
25°C
–40°C to 85°C
–40°C to 125°C
Var_volt
—
—
—
1.0
1.0
1.0
2.0
2.0
2.0
%/V
1. These specifications concern long-term frequency variation. Each measurement is taken over a 1-ms period.
2. Absolute value of variation in ICG output frequency, trimmed at nominal VDD and temperature, as temperature and VDD
are allowed to vary for a single given setting of N.
3. Specification is characterized but not tested.
4. Variation in ICG output frequency for a fixed N and voltage
5. Variation in ICG output frequency for a fixed N
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
188
Freescale Semiconductor
Trimmed Accuracy of the Internal Clock Generator
Figure 17-1 through Figure 17-4 illustrate typical performance. The formula for this variation of frequency
is (measured-nominal)/nominal. Figure 17-1 shows the variation in ICG frequency for a part trimmed at
nominal voltage and temperature across VDD and temperature for a 3-V application with multiply register
(N) set to 1. Figure 17-2 shows 5 V.
6.00%
4.00%
2.7
2.00%
3
0.00%
3.3
-2.00%
-4.00%
-6.00%
-40
25
85
125
2.7
0.00862069
3
0.012931034
-0.004310345 -0.021551724 -0.036637931
0
-0.023706897 -0.034482759
3.3
0.00862069
0
-0.019396552 -0.034482759
Figure 17-1. Example of Frequency Variation Across Temperature,
Trimmed at Nominal 3 Volts, 25°C, and N = 1
6.00%
4.00%
2.7
2.00%
3
0.00%
3.3
-2.00%
-4.00%
-6.00%
-40
25
85
125
2.7
0.021688017
-0.004114642
-0.035937247
-0.054665964
3
0.027728231
0
-0.033768445
-0.055436193
3.3
0.033525215
0.006019945
-0.032552294
-0.055456462
Figure 17-2. Example of Frequency Variation Across Temperature,
Trimmed at Nominal 3 Volts, 25°C, and N = 104
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
189
Electrical Specifications
Figure 17-3 and Figure 17-4 shows N set to 104, hex 68, which corresponds to an ICG frequency of 31.9
MHz or 7.9 MHz bus.
6.00%
4.00%
2.00%
4.5
0.00%
5
5.5
-2.00%
-4.00%
-6.00%
-40
25
85
125
4.5
0.015021459
0.002145923
-0.025751073 -0.036480687
5
0.015021459
0
-0.021459227 -0.034334764
5.5
0.012875536
0.006437768
-0.019313305 -0.030042918
Figure 17-3. Example of Frequency Variation Across Temperature,
Trimmed at Nominal 5 Volts, 25°C, and N = 1
,
,
6.00%
4.5
1.00%
5
5.5
-4.00%
-9.00%
-40
25
85
125
4.5
0.031595514
-0.001573799
-0.045660099
-0.073709584
5
0.045460884
0
-0.052393569
-0.076379066
5.5
0.042572265
-0.009064287
-0.047532721
-0.077255613
Figure 17-4. Example of Frequency Variation Across Temperature,
Trimmed at Nominal 5 Volts, 25°C, and N = 104
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
190
Freescale Semiconductor
Analog-to-Digital Converter (ADC) Characteristics
17.10 Analog-to-Digital Converter (ADC) Characteristics
Characteristic
Symbol
Min
Max
Unit
Notes
Supply voltage
VDD
2.7
5.5
V
Input voltages
VADIN
0
VDD
V
Resolution
BAD
8
8
Bits
Absolute accuracy(1), (2)
AAD
–2.5
+2.5
Counts
8 bits = 256 counts
ADC clock rate
fADIC
500 k
1.048 M
Hz
tAIC = 1/fADIC,
Tested only at 1 MHz
Conversion range
RAD
VSS
VDD
V
Power-up time
tADPU
16
—
tAIC cycles
Conversion time
tADC
16
17
tAIC cycles
Sample time
tADS
5
—
tAIC cycles
Monotocity
MAD
Zero input reading
ZADI
00
—
Hex
VIn = VSS
Full-scale reading
FADI
—
FF
Hex
VIn = VDD
Input capacitance
CADI
—
20
pF
Not tested
Guaranteed
1. One count is 1/256 of VDD.
2. VREFH is shared with VDD. VREFL is shared with VSS.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
191
Electrical Specifications
17.11 Memory Characteristics
Characteristic
Symbol
Min
Typ
Max
Unit
VRDR
1.3
—
—
V
—
1
—
—
MHz
fRead(1)
0
—
8M
Hz
FLASH page erase time
<1 K cycles
>1 K cycles
tErase
0.9
3.6
1
4
1.1
5.5
ms
FLASH mass erase time
tMErase
4
—
—
ms
FLASH PGM/ERASE to HVEN setup time
tNVS
10
—
—
µs
FLASH high-voltage hold time
tNVH
5
—
—
µs
FLASH high-voltage hold time (mass erase)
tNVHL
100
—
—
µs
FLASH program hold time
tPGS
5
—
—
µs
FLASH program time
tPROG
30
—
40
µs
FLASH return to read time
tRCV(2)
1
—
—
µs
FLASH cumulative program HV period
tHV(3)
—
—
4
ms
FLASH endurance(4)
—
10 k
100 k
—
Cycles
FLASH data retention time(5)
—
15
100
—
Years
RAM data retention voltage
FLASH program bus clock frequency
FLASH read bus clock frequency
1. fRead is defined as the frequency range for which the FLASH memory can be read.
2. tRCV is defined as the time it needs before the FLASH can be read after turning off the high voltage charge pump, by clearing HVEN to 0.
3. tHV is defined as the cumulative high voltage programming time to the same row before next erase.
tHV must satisfy this condition: tNVS + tNVH + tPGS + (tPROG x 64) ≤ tHV maximum.
4. Typical endurance was evaluated for this product family. For additional information on how Freescale defines Typical Endurance, please refer to Engineering Bulletin EB619.
5. Typical data retention values are based on intrinsic capability of the technology measured at high temperature and de-rated
to 25°C using the Arrhenius equation. For additional information on how Freescale defines Typical Data Retention, please
refer to Engineering Bulletin EB618.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
192
Freescale Semiconductor
Chapter 18
Ordering Information and Mechanical Specifications
18.1 Introduction
This section contains ordering numbers for MC68HC908KX8 and MC68HC908KX2. Refer to Figure 18-1
for an example of the device numbering system.
In addition, this section gives the package dimensions for:
• 16-pin plastic dual in-line package (case number 648D)
• 16-pin small outline package (case number 751G)
18.2 MC Order Numbers
Table 18-1. MC Order Numbers
MC Order Number(1)
Operating
Temperature Range
MC68HC908KX8CP
MC68HC908KX8CDW
–40°C to +85°C
MC68HC908KX8VP
MC68HC908KX8VDW
–40°C to +105°C
MC68HC908KX8MP
MC68HC908KX8MDW
–40°C to +125°C
MC68HC908KX2CP
MC68HC908KX2CDW
–40°C to +85°C
MC68HC908KX2VP
MC68HC908KX2VDW
–40°C to +105°C
MC68HC908KX2MP
MC68HC908KX2MDW
–40°C to +125°C
1. P = Plastic dual in-line package
DW = Small outline package
MC68HC908KX8XXX
FAMILY
PACKAGE DESIGNATOR
TEMPERATURE RANGE
Figure 18-1. Device Numbering System
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
193
Ordering Information and Mechanical Specifications
18.3 16-Pin Plastic Dual In-Line Package (PDIP)
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
3. DIMENSION L TO CENTER OF LEADS WHEN
FORMED PARALLEL.
4. DIMENSIONS A AND B DO NOT INCLUDE
MOLD PROTRUSION.
5. MOLD FLASH OR PROTRUSIONS SHALL NOT
EXCEED 0.25 (0.010).
6. ROUNDED CORNERS OPTIONAL.
-A16
9
-B1
8
F
L
C
S
SEATING
PLANE
-TK
H
G
M
J
D 16 PL
0.25 (0.010) M T B
S
A
S
DIM
A
B
C
D
F
G
H
J
K
L
M
S
INCHES
MILLIMETERS
MIN
MAX
MIN MAX
0.740 0.760 18.80 19.30
0.245 0.260
6.23
6.60
0.145 0.175
3.69
4.44
0.015 0.021
0.39
0.53
0.050 0.070
1.27
1.77
0.100 BSC
2.54 BSC
0.050 BSC
1.27 BSC
0.008 0.015
0.21
0.38
0.120 0.140
3.05
3.55
0.295 0.305
7.50
7.74
0°
10 °
0°
10 °
0.015 0.035
0.39
0.88
18.4 16-Pin Small Outline Package (SOIC)
A
D
9
1
8
H
h X 45 °
E
0.25
8X
M
B
M
16
θ
16X
M
14X
e
T A
S
B
S
A1
L
A
0.25
B
B
SEATING
PLANE
T
C
NOTES:
1. DIMENSIONS ARE IN MILLIMETERS.
2. INTERPRET DIMENSIONS AND
TOLERANCES PER ASME Y14.5M, 1994.
3. DIMENSIONS D AND E DO NOT INLCUDE
MOLD PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15 PER
SIDE.
5. DIMENSION B DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.13 TOTAL IN
EXCESS OF THE B DIMENSION AT MAXIMUM
MATERIAL CONDITION.
MILLIMETERS
DIM MIN
MAX
A
2.35
2.65
A1 0.10
0.25
B
0.35
0.49
C
0.23
0.32
D 10.15 10.45
E
7.40
7.60
e
1.27 BSC
H 10.05 10.55
h
0.25
0.75
L
0.50
0.90
θ
0°
7°
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
194
Freescale Semiconductor
Appendix A
MC68HC908KX2
A.1 Introduction
This appendix describes the differences between the MC68HC908KX8 and the MC68HC908KX2.
A.2 Functional Description
The MC68HC908KX2 FLASH memory is an array of 2,048 bytes with an additional 36 bytes of user
vectors and one byte used for block protection. See Figure A-1.
NOTE
An erased bit reads as a 1 and a programmed bit reads as a 0.
The program and erase operations are facilitated through control bits in the FLASH control register
(FLCR). See 2.6 FLASH Control Register.
The FLASH is organized internally as an 8-word by 8-bit complementary metal-oxide semiconductor
(CMOS) page erase, byte (8-bit) program embedded FLASH memory. Each page consists of 64 bytes.
The page erase operation erases all words within a page. A page is composed of two adjacent rows.
A security feature prevents viewing of the FLASH contents.(1)
See 2.6 FLASH Control Register for a complete description of FLASH operation.
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
195
MC68HC908KX2
$0000
↓
$003F
$0040
↓
$00FF
$0100
↓
$0FFF
$1000
↓
$13FF
I/O REGISTERS (64 BYTES)
RAM (192 BYTES)
UNIMPLEMENTED (3840 BYTES)
FLASH BURN-IN ROM (1024 BYTES)
$1400
↓
$F5FF
UNIMPLEMENTED (57,856 BYTES)
$F600
↓
$FDFF
USER FLASH MEMORY (2048 BYTES)
$FE00
RESERVED
$FE01
SIM RESET STATUS REGISTER (SRSR)
$FE02
RESERVED
$FE03
RESERVED
$FE04
RESERVED
$FE05
RESERVED
$FE06
RESERVED
$FE07
RESERVED
$FE08
FLASH CONTROL REGISTER (FLCR)
$FE09
BREAK ADDRESS REGISTER HIGH (BRKH)
$FE0A
BREAK ADDRESS REGISTER LOW (BRKL)
$FE0B
BREAK STATUS AND CONTROL REGISTER (BRKSCR)
$FE0C
LVI STATUS REGISTER (LVISR)
$FE0D
↓
$FE1F
UNIMPLEMENTED (19 BYTES)
$FE20
↓
$FF46
MONITOR ROM (295 BYTES)
$FF47
↓
$FF7D
UNIMPLEMENTED (55 BYTES)
$FF7E
FLASH BLOCK PROTECT REGISTER (FLBPR)
$FF7F
↓
$FFDB
UNIMPLEMENTED (93 BYTES)
$FFDC
↓
$FFFF
FLASH VECTORS
(36 BYTES)
Figure A-1. MC68HC908KX2 Memory Map
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
196
Freescale Semiconductor
Appendix B
MC68HC08KX8
B.1 Introduction
This appendix describes the differences between the read-only memory (ROM) version (MC68HC08KX8)
and the FLASH version (MC68HC908KX8) of the microcontroller.
Basically, the differences are:
•
FLASH x ROM module changes
– FLASH for ROM substitution
– Partial use of FLASH-related module
• Configuration register programming
• Wider range of operating voltage
B.2 FLASH x ROM Module Changes
This subsection describes changes between the FLASH and ROM modules.
B.2.1 FLASH for ROM Substitution
FLASH memory and FLASH supporting modules are replaced by ROM memory, see Figure B-1.
In Figure B-1, the user FLASH and user FLASH vector space are respectively substituted by user ROM
and user ROM vector space.
Additionally, these modules and registers have been eliminated in the ROM version:
• FLASH burn-in ROM module — Auxiliary FLASH routine codes
• FLASH charge pump module — High-voltage for FLASH programming
• MENRST module — Helps erased FLASH parts programming, see 13.3.1.5 Forced Monitor Mode
Entry Reset (MENRST)
• SIM reset status register, bit 2 — Refers to MENRST. See 13.7.1 SIM Reset Status Register.
MENRST has no function in the ROM version and reading this bit will return 0.
• FLASH test control register, FLTCR
• FLASH control register, FLCR
• FLASH block protect register, FLBPR
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
197
Freescale Semiconductor
SECURITY
MODULE
USER ROM — 7680 BYTES
COMPUTER OPERATING PROPERLY
MODULE
LOW-VOLTAGE INHIBIT
MODULE
MONITOR ROM — 296 BYTES
2-CHANNEL TIMER INTERFACE
MODULE
USER ROM VECTOR SPACE — 36 BYTES
KEYBOARD INTERRUPT
MODULE
INTERNAL CLOCK GENERATOR
MODULE
SOFTWARE SELECTABLE
SYSTEM INTEGRATION
MODULE
IRQ
MODULE
IRQ1 (1)
VDD
VSS
POWER
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATION INTERFACE
MODULE
PROGRAMMABLE TIMEBASE
MODULE
SINGLE BRKPT BREAK
MODULE
Notes:
1. Pin contains integrated pullup resistor.
2. High-current source/sink pin
3. Pin contains software selectable pullup resistor if general function I/O pin is configured as input.
4. Pins are used for external clock source or crystal/ceramic resonator option.
Figure B-1. M68HC08KX8 MCU Block Diagram
DDRA
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
PTA0/KBD0(2), (3)
PTA1/KBD1(2), (3)
PTA2/KBD2/TCH0(2), (3)
PTA3/KBD3/TCH1(2), (3)
PTA4/KBD4 (2), (3)
POWER-ON RESET
MODULE
CONTROL AND STATUS REGISTERS — 78 BYTES
USER RAM — 192 BYTES
PTB
ARITHMETIC/LOGIC
UNIT
DDRB
CPU
REGISTERS
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
PTB5/TxD
PTB6/(OSC1)(4)
PTB7/(OSC2)(4)
PTA
M68HC08 CPU
MC68HC08KX8
198
INTERNAL BUS
Configuration Register Programming
B.2.2 Partial Use of FLASH-Related Module
16.3 Monitor ROM (MON) was written having FLASH as user memory and user vector space.
MON functions are maintained for the ROM version. MON will allow execution of code in random-access
memory (RAM) or ROM and provide ROM memory security(1). The memory programming interface,
though, will have no effect in ROM version.
An assumption that must be made for the ROM version is that the reset vector will always have a value
different from $0000, corresponding to the user code start address. For this reason, force entry into
monitor mode, described in 16.3.1.1 Monitor Mode Entry and in 16.3.1.3 Forced Monitor Mode, is not
applicable to the ROM version. The MENRST module has been eliminated from the ROM version.
The security function described in 16.3.2 Security also applies to the user ROM memory for the ROM
version.
B.3 Configuration Register Programming
Functionally, the terms MOR (mask option register) and CONFIG (configuration register) can be used
interchangeably. MOR and CONFIG are equivalent since both define the same module functionality
options through the registers bits. As a naming convention, though, configuration registers are named
MOR for a ROM version and CONFIG for a FLASH version.
Some modules affected by the configuration register bits make reference to default values of these bits
and have recommendation notes on programming them.
For specific information see:
• FLASH — 2.5 FLASH Memory (FLASH)
• ICG — 7.6 CONFIG (or MOR) Register Options
• LVI — 10.3 Functional Description
• PORT — 11.3.1 Port B Data Register
• COP — 5.4.7 COPD (COP Disable) and 5.4.8 COPRS (COP Rate Select)
• CONFIG — 4.2 Functional Description
NOTE
The user must keep in mind that these notes are not entirely applicable to
the MOR found in the ROM version. The MOR bits can neither assume the
described CONFIG default values after reset nor can they be modified later
under user code control. While the MOR is mask defined, and consequently
unwritable, CONFIG can be written once after each reset.
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the ROM difficult for
unauthorized users.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
199
MC68HC08KX8
Address: $001E
Read:
Write:
Bit 7
6
5
4
3
2
1
Bit 0
R
LVI2
EXTXTALEN
EXTSLOW
EXTCLKEN
0
OSCEINSTOP
SCIBDSRC
Reset:
Unaffected by reset
R
= Reserved
Figure B-2. Mask Option Register 2 (MOR2)
Address: $001F
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
COPRS
LVISTOP
LVIRSTD
LVIPWRD
LVI5OR3
SSREC
STOP
COPD
Unaffected by reset
Figure B-3. Mask Option Register 1 (MOR1)
NOTE
With the FLASH charge pump eliminated, MOR2 bit 2 (originally
PMPREGD in CONFIG) has no effect. Reading this bit will return 0. For a
complete description of other configuration bits, refer to 4.2 Functional
Description.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
200
Freescale Semiconductor
Electrical Specifications
B.4 Electrical Specifications
This subsection contains electrical and timing specifications for the MC68HC08KX8.
B.4.1 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the microcontroller unit (MCU) can be exposed without
permanently damaging it.
NOTE
This device is not guaranteed to operate properly at the maximum ratings.
Refer to B.4.4 5.0-Vdc DC Electrical Characteristics, and for guaranteed
operating conditions.
Characteristic(1)
Symbol
Value
Unit
Supply voltage
VDD
–0.3 to +6.0
V
Input voltage
VIn
VSS –0.3 to VDD +0.3
V
I
±15
mA
IPTA0–IPTA4
±25
mA
Maximum current out of VSS
IMVSS
100
mA
Maximum current into VDD
IMVDD
100
mA
Storage temperature
TSTG
–55 to +150
°C
Maximum current per pin
Excluding VDD, VSS, and PTA0–PTA4
Maximum current for pins
PTA0–PTA4
1. Voltages referenced to VSS
NOTE
This device contains circuitry to protect the inputs against damage due to
high static voltages or electric fields; however, it is advised that normal
precautions be taken to avoid application of any voltage higher than
maximum-rated voltages to this high-impedance circuit. For proper
operation, it is recommended that VIn and VOut be constrained to the range
VSS ≤ (VIn or VOut) ≤ VDD. Reliability of operation is enhanced if unused
inputs are connected to an appropriate logic voltage level (for example,
either VSS or VDD).
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
201
MC68HC08KX8
B.4.2 Functional Operating Range
Characteristic
Symbol
Value
Unit
TA
–40 to 105
°C
VDD
3.0 ± 10%
5.0 ± 10%
V
Symbol
Value
Unit
Thermal resistance
PDIP (16 pins)
SOIC (16 pins)
θJA
66
95
°C/W
I/O pin power dissipation
PI/O
User determined
W
Power dissipation(1)
PD
PD = (IDD x VDD) + PI/O =
K/(TJ + 273°C)
W
Constant(2)
K
Average junction temperature
Operating temperature range
Operating voltage range
B.4.3 Thermal Characteristics
Characteristic
Maximum junction temperature
PD x (TA + 273°C)
+ PD2 x θJA
W/°C
TJ
TA + (PD x θJA)
°C
TJM
125
°C
1. Power dissipation is a function of temperature.
2. K is a constant unique to the device. K can be determined for a known TA and measured PD. With this value of K, PD and
TJ can be determined for any value of TA.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
202
Freescale Semiconductor
Electrical Specifications
B.4.4 5.0-Vdc DC Electrical Characteristics
Characteristic(1)
Symbol
Min
Typ(2)
Max
VDD –0.4
VDD –1.5
VDD –0.8
—
—
—
—
—
—
—
—
—
—
—
—
0.4
1.5
0.8
Unit
Output high voltage
ILoad = –2.0 mA, all I/O pins
ILoad = –10.0 mA, all I/O pins
ILoad = –15.0 mA, PTA0–PTA4 only
VOH
Output low voltage
ILoad = 1.6 mA, all I/O pins
ILoad = 10.0 mA, all I/O pins
ILoad = 15.0 mA, PTA0–PTA4 only
VOL
Input high voltage — all ports, IRQ1
VIH
0.7 x VDD
—
VDD + 0.3
V
Input low voltage — all ports, IRQ1
VIL
VSS
—
0.3 x VDD
V
—
—
—
16.6
1.9
0.8
20
5
1.75
mA
mA
µA
V
V
VDD supply current
Run(3), (4)
Wait(4), (5)
Stop, 25°C(4), (6)
IDD
I/O ports Hi-Z leakage current(7)
IIL
–10
—
+10
µA
Input leakage current
IIn
–1.0
—
+1.0
µA
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
POR rearm voltage(8)
VPOR
0
—
100
mV
POR reset voltage(9)
VPOR
0
700
800
mV
POR rise time ramp rate
RPOR
0.035
—
—
V/ms
Monitor mode entry voltage
VTST
VDD+ 2.5
VDD+ 4.0
V
Low-voltage inhibit reset, trip falling voltage
VTRIPF
3.90
4.3
4.50
V
Low-voltage inhibit reset, trip rising voltage
VTRIPR
4.00
4.4
4.60
V
Low-voltage inhibit reset/recover hysteresis
VHYS
—
100
—
mV
Pullup resistor
PTA0–PTA4, IRQ1
RPU
24
—
48
kΩ
1. VDD = 5.5 Vdc to 4.5 Vdc, VSS = 0 Vdc, TA = –40°C to +85°C, unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using internal oscillator at its 32-MHz rate. VDD = 5.5 Vdc. All inputs 0.2 V from rail. No dc
loads. Less than 100 pF on all outputs. All ports configured as inputs. Measured with all modules enabled.
4. All measurements taken with LVI enabled.
5. Wait IDD measured using internal oscillator at its 1-MHz rate. All inputs 0.2 V from rail; no dc loads; less than 100 pF on all
outputs. All ports configured as inputs.
6. Stop IDD is measured with no port pin sourcing current; all modules are disabled. OSCSTOPEN option is not selected.
7. Pullups and pulldowns are disabled.
8. Maximum is highest voltage that POR is guaranteed.
9. Maximum is highest voltage that POR is possible.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
203
MC68HC08KX8
B.4.5 3.0-Vdc DC Electrical Characteristics
Characteristic(1)
Symbol
Min
Typ(2)
Max
VDD –0.3
VDD –1.0
VDD –0.6
—
—
—
—
—
—
—
—
—
—
—
—
0.3
1.0
0.6
V
V
V
Unit
Output high voltage
ILoad = –0.6 mA, all I/O pins
ILoad = –4.0 mA, all I/O pins
ILoad = –10 mA, PTA0–PTA4 only
VOH
Output low voltage
ILoad = 0.5 mA, all I/O pins
ILoad = 6.0 mA, all I/O pins
ILoad = 10 mA, PTA0–PTA4 only
VOL
Input high voltage — all ports, IRQ1
VIH
0.7 x VDD
—
VDD + 0.3
V
Input low voltage — all ports, IRQ1
VIL
VSS
—
0.3 x VDD
V
—
—
—
4.4
1
0.65
10
2.5
1.25
mA
mA
µA
V
VDD supply current
Run(3), (4)
Wait(4), (5)
Stop, 25°C(4), (6)
IDD
I/O ports Hi-Z leakage current(7)
IIL
–10
—
+10
µA
Input leakage current
IIn
–1.0
—
+1.0
µA
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
POR rearm voltage(8)
VPOR
0
—
100
mV
POR reset voltage(9)
VPOR
0
700
800
mV
POR rise time ramp rate
RPOR
0.02
—
—
V/ms
Monitor mode entry voltage
VTST
VDD+ 2.5
—
VDD+ 4.0
V
Low-voltage inhibit reset, trip falling voltage
VTRIPF
2.4
2.60
2.70
V
Low-voltage inhibit reset, trip rising voltage
VTRIPR
2.5
2.68
2.80
V
Low-voltage inhibit reset/recover hysteresis
VHYS
—
80
—
mV
Pullup resistor
PTA0–PTA4, IRQ1
RPU
24
—
48
kΩ
1. VDD = 3.3 to 2.7 Vdc, VSS = 0 Vdc, TA = –40°C to +85°C, unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using internal oscillator at its 16-MHz rate. VDD = 3.3 Vdc. All inputs 0.2 V from rail. No dc
loads. Less than 100 pF on all outputs. All ports configured as inputs. Measured with all modules enabled.
4. All measurements taken with LVI enabled.
5. Wait IDD measured using internal oscillator at its 1 MHz rate. All inputs 0.2 V from rail; no dc loads; less than 100 pF on all
outputs. All ports configured as inputs.
6. Stop IDD is measured with no port pins sourcing current; all modules are disabled.
7. Pullups and pulldowns are disabled.
8. Maximum is highest voltage that POR is guaranteed.
9. Maximum is highest voltage that POR is possible.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
204
Freescale Semiconductor
Electrical Specifications
B.4.6 Internal Oscillator Characteristics
Characteristic(1)
Internal oscillator base frequency(2), (3)
Internal oscillator tolerance
Internal oscillator multiplier(4)
Symbol
Min
Typ
Max
Unit
fINTOSC
230.4
320
384
kHz
fOSC_TOL
–25
—
+25
%
N
1
—
127
—
1. VDD = 5.5 Vdc to 2.7 Vdc, VSS = 0 Vdc, TA = –40°C to +85°C, unless otherwise noted
2. Internal oscillator is selectable through software for a maximum frequency. Actual frequency will be multiplier (N) x base
frequency.
3. fBus = (fINTOSC / 4) x N when internal clock source selected
4. Multiplier must be chosen to limit the maximum bus frequency of 4 MHz for 2.7-V operation and 8 MHz for 4.5-V operation.
B.4.7 External Oscillator Characteristics
Characteristic(1)
Symbol
Min
Typ
Max
dc(5)
—
32 M(6)
60
307.2 k
—
—
307.2 k
32 M(6)
Unit
External clock option(2), (3)
With ICG clock disabled
With ICG clock enabled
EXTSLOW = 1(4)
EXTSLOW = 0(4)
fEXTOSC
External crystal options(7), (8)
EXTSLOW = 1(4)
EXTSLOW = 0(4)
fEXTOSC
30 k
1M
—
—
100 k
8M
Hz
Crystal load capacitance(9)
CL
—
—
—
pF
Crystal fixed capacitance(9)
C1
—
2 x CL
—
pF
Crystal tuning capacitance(9)
C2
—
2 x CL
—
pF
Feedback bias resistor(9)
RB
—
10
—
MΩ
Series resistor (9), (10)
RS
—
—
—
MΩ
Hz
1.
2.
3.
4.
VDD = 5.5 to 2.7 Vdc, VSS = 0 Vdc, TA = –40°C to +85°C, unless otherwise noted
Setting EXTCLKEN configuration option enables OSC1 pin for external clock square-wave input.
No more than 10% duty cycle deviation from 50%
EXTSLOW configuration option configures external oscillator for a slow speed crystal and sets the clock monitor circuits
of the ICG module to expect an external clock frequency that is higher/lower than the internal oscillator base frequency,
fINTOSC.
5. Some modules may require a minimum frequency greater than dc for proper operation. See appropriate table for this
information.
6. MCU speed derates from 32 MHz at VDD = 4.5 Vdc to 16 MHz at VDD = 2.7 Vdc.
7. Setting EXTCLKEN and EXTXTALEN configuration options enables OSC1 and OSC2 pins for external crystal option.
8. fBus = (fEXTOSC / 4) when external clock source is selected.
9. Consult crystal vendor data sheet, see Figure 7-3. External Clock Generator Block Diagram.
10. Not required for high-frequency crystals
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
205
MC68HC08KX8
B.4.8 Trimmed Accuracy of the Internal Clock Generator
The unadjusted frequency of the low-frequency base clock (IBASE), when the comparators in the
frequency comparator indicate zero error, can vary as much as ±25% due to process, temperature, and
voltage. The trimming capability exists to compensate for process affects. The remaining variation in
frequency is due to temperature, voltage, and change in target frequency (multiply register setting). These
affects are designed to be minimal, however variation does occur. Better performance is seen at 3 V and
lower settings of N.
B.4.8.1 2.7-Volt to 3.3-Volt Trimmed Internal Clock Generator Characteristics
Characteristic(1)
Symbol
Min
Typ
Max
Unit
Absolute trimmed internal oscillator tolerance(2), (3)
–40°C to 85°C
Fabs_tol
—
1.5
5.0
Variation over temperature(3), (4)
Var_temp
—
0.03
0.05
%/C
Variation over voltage(3), (5)
25°C
–40°C to 85°C
Var_volt
—
—
0.5
0.7
2.0
2.0
%/V
%
1. These specifications concern long-term frequency variation. Each measurement is taken over a 1-ms period.
2. Absolute value of variation in ICG output frequency, trimmed at nominal VDD and temperature, as temperature and VDD
are allowed to vary for a single given setting of N.
3. Specification is characterized but not tested.
4. Variation in ICG output frequency for a fixed N and voltage
5. Variation in ICG output frequency for a fixed N
B.4.8.2 4.5-Volt to 5.5-Volt Trimmed Internal Clock Generator Characteristics
Characteristic(1)
Symbol
Min
Typ
Max
Unit
Absolute trimmed internal oscillator tolerance(2), (3)
–40°C to 85°C
Fabs_tol
—
4.0
7.0
Variation over temperature(3), (4)
Var_temp
—
0.05
0.08
%/C
Variation over voltage(3), (5)
25°C
–40°C to 85°C
Var_volt
—
—
1.0
1.0
2.0
2.0
%/V
%
1. These specifications concern long-term frequency variation. Each measurement is taken over a 1-ms period.
2. Absolute value of variation in ICG output frequency, trimmed at nominal VDD and temperature, as temperature and VDD
are allowed to vary for a single given setting of N.
3. Specification is characterized but not tested.
4. Variation in ICG output frequency for a fixed N and voltage
5. Variation in ICG output frequency for a fixed N
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
206
Freescale Semiconductor
Electrical Specifications
B.4.9 Analog-to-Digital Converter (ADC) Characteristics
Characteristic
Symbol
Min
Max
Unit
Notes
Supply voltage
VDD
2.7
5.5
V
Input voltages
VADIN
0
VDD
V
Resolution
BAD
8
8
Bits
Absolute accuracy(1), (2)
AAD
–2.5
+2.5
Counts
8 bits = 256 counts
ADC clock rate
fADIC
500 k
1.048 M
Hz
tAIC = 1/fADIC,
Tested only at 1 MHz
Conversion range
RAD
VSS
VDD
V
Power-up time
tADPU
16
—
tAIC cycles
Conversion time
tADC
16
17
tAIC cycles
Sample time
tADS
5
—
tAIC cycles
Monotocity
MAD
Zero input reading
ZADI
00
—
Hex
VIn = VSS
Full-scale reading
FADI
—
FF
Hex
VIn = VDD
Input capacitance
CADI
—
20
pF
Not tested
Guaranteed
1. One count is 1/256 of VDD.
2. VREFH is shared with VDD. VREFL is shared with VSS.
B.4.10 Memory Characteristics
Characteristic
RAM data retention voltage(1)
Symbol
Min
Max
Units
VRDR
1.3
—
V
1. Specification is characterized but not tested.
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
Freescale Semiconductor
207
MC68HC08KX8
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
208
Freescale Semiconductor
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